Case history comments

Published on 02/03/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 1120 times

Case history comments

This is low for a young male.

When it was discovered that the urine collection was for 17 hours and not 24 hours, his urine flow-rate was recalculated (2160/1020):

Recalculating his creatinine clearance:

This is in the range one would expect in a young male. One can see, therefore, how errors in the timing and collection of urine significantly influence the calculation of the creatinine clearance. Errors in collection are by far the most common and serious errors encountered when estimating the creatinine clearance.

Case history 10

One can make a confident diagnosis of central diabetes insipidus from the history of head trauma and the observation that she was producing large volumes of urine and complaining of thirst. Her blood glucose level excludes diabetes mellitus as a cause of her polyuria and her hypernatraemia accounts for her thirst. In normal circumstances a serum sodium concentration of 150 mmol/L will stimulate AVP production and cause the urine to be maximally concentrated. This patient’s urine is, therefore, inappropriately dilute. It would be unnecessary and even dangerous to attempt to perform a water deprivation test on this patient. Note that her serum urea is not increased. This reflects her high urine flow-rate despite her significant water depletion.

Case history 11

The patient is on a low-carbohydrate diet in order to lose weight. His carbohydrate intake is so low that he is having to use up adipose tissue supplies of fatty acids to produce enough energy. Ketone bodies are produced and released as part of this process.

Case history 12

The most useful piece of information here is the finding of pitting oedema, because it considerably narrows the differential diagnosis of proteinuria, which would otherwise be extensive. The combination of proteinuria and pitting oedema could be explained by the nephrotic syndrome, in which protein loss in the urine results in hypoalbuminaemia. However, congestive cardiac failure is the most likely explanation. It is much commoner than nephrotic syndrome, and is frequently associated with proteinuria.

Case history 13

The marked increase in the serum urea with the modest increase in the serum creatinine would indicate the presence of pre-renal uraemia. Pyrexial patients are frequently hypercatabolic, which will contribute to his high serum urea. His low serum bicarbonate and high anion gap indicates that he has a metabolic acidosis. This acidosis will cause the potassium to move from the intracellular to the extracellular compartment. The reduction in his glomerular filtration rate results in his inability to maintain a normal serum potassium in the face of this efflux as both these factors contribute to his hyperkalaemia.

Case history 14

The serum urea in this case, though high, is relatively low in comparison to the serum creatinine. This would be consistent with a low protein intake. The serum bicarbonate is low, indicating the presence of a metabolic acidosis. However, the anion gap is normal and, hence, it is unlikely that this patient’s [H⁺] will be grossly abnormal. The hyperkalaemia, therefore, is likely to be entirely due to the low glomerular filtration rate with the efflux of potassium from the intracellular to the extracellular compartment being of minor importance. The hyponatraemia in this case reflects impaired water excretion resulting from the inability of the renal tubules to respond to AVP. These results clearly indicate that the patient needs to continue with dialysis. This woman’s serum calcium status should also be assessed. Hypocalcaemia should be excluded and a high serum alkaline phosphatase would indicate the presence of metabolic bone disease. A raised serum PTH concentration is another very sensitive marker of metabolic bone disease in patients with renal failure.

Treatment of metabolic bone disease in renal failure is aimed at correcting hypocalcaemia and hyperphosphataemia, e.g. oral calcium salts and calcitriol (active form of vitamin D).

Case history 15

The low [H⁺] and high bicarbonate concentration confirm that this patient has a metabolic alkalosis. The raised PCO₂ indicates partial respiratory compensation for this. The loss of H⁺ will have been caused by his severe vomiting which, in view of the history, is likely to be due to pyloric stenosis. Ingestion of bicarbonate would not lead to this degree of metabolic alkalosis though it will have aggravated the situation. The severe vomiting has led to dehydration and this is manifested by the presence of pre-renal uraemia. The hypokalaemia is due to a combination of potassium loss in the vomitus and the metabolic alkalosis causing the influx of potassium from the ECF to the ICF.

The urine results are typical of a patient with dehydration and metabolic alkalosis due to vomiting. Aldosterone is being secreted in an attempt to expand his ECF and the patient is conserving sodium despite his hypernatraemia. The hyperaldosteronism is promoting potassium loss despite hypokalaemia, and hydrogen ion loss, resulting in the classical paradoxical acid urine.

Case history 16

The high [H⁺] and PCO₂ confirm the presence of a respiratory acidosis which, from the history, will have been expected. Note that the bicarbonate is not abnormally increased, which indicates that this is an acute development, and renal compensation for the respiratory acidosis has not had time to have a significant impact on the respiratory acidosis.

Case history 17

The [H⁺] is at the upper end of the reference interval. The PCO₂ is markedly elevated which would indicate the presence of a respiratory acidosis but the bicarbonate concentration is also markedly increased as the compensatory response for the respiratory acidosis. This man has type 2 respiratory failure.

Case history 18

The dominant feature in this patient’s acid–base disorder is an alkalosis as the [H⁺] is low. The bicarbonate concentration is increased, indicating a metabolic alkalosis. The PCO₂ is increased (respiratory acidosis) and this could be due to partial compensation for the metabolic alkalosis. However, the increase in PCO₂ is too high for this to be the only explanation. The background history of respiratory disease is the other reason for this patient’s respiratory acidosis.

The PO₂ indicates that the patient is satisfactorily oxygenating her blood.

This patient’s hypokalaemia and metabolic alkalosis can be explained by profound potassium depletion due to the use of a diuretic with an inadequate intake of potassium. The principles of therapy are potassium supplementation and alteration of her drug regimen to one that will ameliorate potassium loss, e.g. use of an ACE inhibitor.

Case history 19

By far the most likely diagnosis based on the information given is the nephrotic syndrome. In the nephrotic syndrome you would expect the serum albumin to be low and the urinary albumin to be high. The serum urea and electrolytes are frequently normal. Although the glomerular basement membrane may be damaged, the glomerular filtration rate is usually normal in the early stages of the nephrotic syndrome. Hypercholesterolaemia is a feature of the nephrotic syndrome. The history of recurrent infections suggests a degree of immune deficiency. This patient is likely to be losing immunoglobulin and some of the components of the complement system in her urine and this could lead to a relative immune deficiency.

Case history 20

This man is suffering from multiple myeloma. He is one of the approximately 20% of patients with myeloma that do not have a paraprotein in the serum but have Bence Jones proteinuria. His renal function should be tested and hypercalcaemia should be excluded.

Case history 21

This man’s presentation is typical of an acute coronary syndrome which may be the manifestation of a full blown myocardial infarction in this case. He should have an ECG recorded as soon as possible which may, in combination with the history, confirm the diagnosis of an MI. His plasma troponin should be measured, though this may not be increased in patients with an acute coronory syndrome until 12 hours after the onset of pain.

Case history 22

Metastatic breast carcinoma is the most likely diagnosis in this case. The liver function tests indicate that there is little hepatocellular damage present and that bilirubin excretion is normal. These findings, however, do not exclude the possibility of hepatic metastasis, giving rise to localized areas of intrahepatic obstruction. If this were so, then the γGT should also be increased. A normal serum calcium does not exclude the possibility of bone metastasis, which is another source of the high alkaline phosphatase activity. This could be confirmed by studying alkaline phosphatase isoenzymes. A third possibility is that there may be a local recurrence with the tumour itself producing alkaline phosphatase, though this would be very unlikely. A bone scan would be very helpful in this case.

Case history 23

In this case, the most likely diagnosis is carcinoma of the head of the pancreas obstructing the common bile duct. The other major differential would be enlarged lymph nodes at the porta hepatis obstructing the common bile duct, which would explain the clinical picture as well as pancreatic cancer. This could result from any abdominal or haematological malignancy, e.g. hepatoma (he was a moderate drinker) or lymphoma. Other differentials include cholangiocarcinoma and gall stones, although these are unlikely. Carcinoma of the head of the pancreas classically gives rise to severe, painless, deep jaundice, which is in keeping with a bilirubin of 250 µmol/L. This is uncomplicated obstructive jaundice, which is characterized by an alkaline phosphatase activity that is more than three times the upper limit of the reference interval. The aspartate and alanine aminotransferase activities do not indicate severe hepatocellular damage. By far the most important further investigations to be performed on this patient would be to image the structures in the vicinity of the head of the pancreas and the common bile duct looking for the cause of the obstruction. This could be done by ultrasound or radiology.

Case history 24

The most striking features of these results are the marked increase in the aspartate and alanine aminotransferase activities. These indicate the presence of acute hepatocellular damage. There is a degree of cholestasis as indicated by the increase in bilirubin associated with an increase in the serum alkaline phosphatase activity. As the increase in alkaline phosphatase is less than twice the upper limit of the reference interval, cholestasis is unlikely to be the dominant cause of the jaundice. The increase in the γGT is to be expected as this enzyme is increased in many forms of liver disease.

The differential diagnosis here includes viral hepatitis or alcoholic hepatitis. An idiosyncratic drug reaction is also possible.

Case history 25

Repeat the fasting blood glucose. The diagnosis of diabetes mellitus is not confirmed until specimens collected on at least two separate occasions place the patient in the diabetic category.

Case history 26

By far the most likely diagnosis in this case is diabetic ketoacidosis. This may be precipitated by a number of conditions, such as infection. This may have caused anorexia and, thus, the patient may have omitted to take her insulin. Trauma can increase a patient’s requirement for insulin but there is nothing to suggest that in this case. The blood glucose can be checked at the bedside as can a specimen of urine for the presence of ketones. The laboratory tests that may be requested are urea and electrolytes to assess renal function, the presence or absence of hyperkalaemia and the serum sodium concentration. The patient’s acid–base status should be assessed to quantitate the severity of the acidosis present, and the blood glucose should be accurately measured. These results will influence the patient’s treatment. It is essential in cases such as this that samples of blood and urine and, if appropriate, sputum are sent to the microbiological laboratory to look for the presence of infection.

Case history 27

Nocturnal hypoglycaemia is the most likely cause of this woman’s symptoms. The diagnosis can be made by measuring her blood glucose while she is symptomatic. However, this can be distressing to patients and is not always feasible. Indirect evidence of nocturnal hypoglycaemia may be obtained by measuring her urinary catecholamine excretion or urinary cortisol excretion overnight. A further clue may be obtained if the woman’s glycated haemoglobin level indicates good diabetic control in the face of hyperglycaemia during the day. In many such cases a diagnosis of nocturnal hypoglycaemia is inferred if the symptoms are relieved by changing the insulin regimen or getting the patient to eat more food before she retires at night.

Case history 28

As renal failure is the most common cause of hypocalcaemia, her serum urea and electrolytes should be measured. However, unsuspected renal failure is unlikely as her serum phosphate is normal. Her plasma PTH should be measured and if high (appropriate to the low calcium) then vitamin D deficiency is the most likely diagnosis, and the cause should be sought. In particular, a detailed dietary history should be taken. An increased serum alkaline phosphatase would be compatible with vitamin D deficiency. The bone pain is due to the underlying osteomalacia.

A low PTH would indicate hypoparathyroidism. Other causes of hypocalcaemia would be unlikely in this case.

Case history 29

The two most likely diagnoses in this case are primary hyperparathyroidism and hypercalaemia of malignancy. The most important biochemical investigation to be performed at this stage would be plasma PTH measurement, which will be high in primary hyperparathyroidism and suppressed in hypercalcaemia of malignancy. In patients with hypercalcaemia of malignancy, the underlying disease is usually detectable by a careful clinical history and examination. There are, however, notable exceptions, multiple myeloma being one, and therefore a sample of serum and urine should be sent for protein electrophoresis to see if a paraprotein band can be identified. A blanket request for tumour markers such as CEA or AFP should not be requested unless there is a clear clinical indication for doing so. The patient’s alkaline phosphatase activity should be measured and alkaline phosphatase isoenzyme studies may be indicated, especially if the plasma PTH concentration is suppressed.

The patient shows evidence of dehydration and has severe hypercalcaemia, which should be treated by rehydration in the first instance.

Case history 30

Though this patient is hypocalcaemic, the expected compensatory rise in PTH may not occur in view of the severe hypomagnesaemia. Thus, the PTH may be low.

This patient needs magnesium supplements. As magnesium salts cause diarrhoea they need to be given parenterally, especially in this case where there is established diarrhoea and malabsorption. It is likely that once the patient is magnesium replete, her original vitamin D and calcium supplements will be sufficient to maintain her in a normocalcaemic state. However, she may require regular ‘top-ups’ of intravenous magnesium in the future.

Case history 31

As Paget’s disease can be considered a disorder of bone remodelling, the serum alkaline phosphatase, which is a good marker of osteoblastic activity, can be used to monitor the disease activity. It cannot, however, be used to demonstrate the involvement of a specific bone or deformity; this has to be done radiologically. If a patient is being given a bisphosphonate it is important to monitor the serum calcium, as hypocalcaemia is a well-recognized side effect of these drugs.

Case history 32

If panhypopituitarism is suspected, a lower dose of insulin should be used. This is because the relative deficiency of glucocorticoids and growth hormone is associated with an increase in insulin sensitivity.

The basal prolactin was so high in this case that prolactinoma was the diagnosis until proven otherwise. Imaging of his pituitary confirmed the diagnosis.

The hypoglycaemic stress induced in this patient did not cause the expected rise in serum cortisol. It is essential, therefore, that he is commenced on steroid replacement before surgery. His low free T₄ combined with the abnormal response in his TSH (i.e. the 60 minute level being greater than the 30 minute level) would support a diagnosis of secondary hypothyroidism. He should, therefore, also be commenced on thyroxine replacement. As prolactinomas frequently shrink dramatically in response to dopamine agonists, he should be commenced preoperatively on either bromocriptine or cabergoline to reduce the size of the tumour.

Case history 33

Growth hormone deficiency should be suspected particularly in view of the documented fall-off in the patient’s growth rate over the previous year. Random GH measurement is potentially misleading – false-positive and false-negative results are frequent. Many endocrinologists measure stimulated GH; a result >6 µg/L excludes GH deficiency.

Case history 34

This patient has a high serum T₄ because the oestrogen component of hormone replacement therapy stimulates the synthesis of thyroxine-binding globulin. Thus, to maintain a normal level of the physiologically active free T₄ the total serum T₄ needs to be increased. The measured free T₄ is likely to be within reference limits.

By far the most important investigation for this woman is a fine-needle aspiration biopsy of the thyroid nodule. Frequently, cystic lesions will be drained by this procedure and may not recur. It is important, however, that adequate thyroid epithelium be obtained to enable the diagnosis of thyroid cancer to be excluded or confirmed.

Case history 35

The low free T₄ and markedly elevated TSH results suggest primary hypothyroidism. Skeletal and cardiac muscles are affected in hypothyroidism, causing the release of creatine kinase into the circulation. This, combined with a decrease in the catabolic rate of creatine kinase, will be sufficient to cause the creatine kinase to increase to the levels observed in this case. The aspartate aminotransferase is mildly elevated and this will fall along with the creatine kinase and cholesterol after a few weeks’ treatment with thyroxine. In view of the evidence of myocardial ischaemia it is prudent to introduce thyroxine replacement cautiously (a low dose would be no more than 50 µg daily). High initial doses can precipitate myocardial ischaemia, and where the hypothyroidism is severe, as in this case, pericardial effusions and impaired ventricular function.

Case history 36

It is likely that this patient has suffered a relapse of her thyrotoxicosis. The severity of the derangement in her thyroid biochemistry (free T₄ 66 pmol/L) makes it likely that she will be clinically thyrotoxic and symptomatic.

Repeated failure of medical therapy may warrant consideration of alternative treatment options, namely radioactive iodine and surgery. The former ablates the production of thyroid hormones irreversibly, and the patient would need to take replacement thyroxine therapy permanently thereafter.

Case history 37

Whenever one encounters the combination of hyponatraemia with hyperkalaemia, adrenocortical failure must be suspected. There is a modest increase in the serum creatinine with a normal serum urea that is not typical of Addison’s disease. In adrenal failure the patient usually has pre-renal uraemia, which causes the serum urea to rise more than the creatinine. The low serum bicarbonate is a feature of adrenal insufficiency, and may reflect both the lack of mineralocorticoid activity and lactic acidosis, the latter resulting from hypovolaemia and associated reduced tissue perfusion.

It is essential that, at the very least, a timed random cortisol is requested on this patient. Unless the result is grossly elevated, thus excluding adrenal insufficiency, a Synacthen test is warranted. As the patient has severe skeletal muscle pain the creatine kinase should be measured as the hyperkalaemia may be due to potassium released from damaged muscle. If rhabdomyolysis were detected, it would be important to monitor renal function and calcium status carefully.

Case history 38

This presentation is classical of acute adrenal failure with characteristic symptoms, physical findings and electrolyte pattern. The diagnosis is confirmed by the Synacthen test.

On presentation, this woman was sodium depleted with pre-renal uraemia. As her ECF was expanded with 0.9% sodium chloride, this improved her glomerular filtration rate, which is sufficient, even in the absence of aldosterone, to correct the hyperkalaemia by increasing her urinary potassium excretion. The reduction in this patient’s blood volume will stimulate vasopressin secretion, giving rise to the hyponatraemia. The sodium chloride infusion by restoring her blood volume will inhibit AVP secretion, enabling her to correct the hyponatraemia.

Case history 39

Cushing’s syndrome is the most likely diagnosis in this case. One can be confident of the diagnosis in view of the increased urinary cortisol : creatinine ratio, and the failure to suppress with low-dose dexamethasone.

Establishing a diagnosis of Cushing’s syndrome is insufficient as it is essential to discover the underlying cause to enable the correct treatment to be given. This patient should have a high-dose dexamethasone suppression test with measurement of serum cortisol and ACTH. Suppression of the cortisol would point to the pituitary-dependent Cushing’s syndrome as would an abnormally increased ACTH concentration. An adenoma should be actively sought in her pituitary and adrenal glands by CT or MRI scanning. If her ACTH is abnormally increased she may undergo selective venous catheterization to locate the source, which may be due to a carcinoid tumour of the lung.

Case history 40

This clinical presentation combined with biochemical findings of increased testosterone, reduced SHBG and increased LH/FSH ratio are characteristic of the polycystic ovarian syndrome. Ultrasound examination of her ovaries would confirm the diagnosis. Patients with obesity and/or PCOS are insulin resistant. This stimulates compensatory hyperinsulinaemia. In many insulin-resistant women, the ovaries remain relatively more insulin sensitive than other tissues, and the hyperinsulinaemia stimulates ovarian androgen production.

Case history 41

An accurate measurement of height and serial measurements of weight are the most important means of monitoring the nutritional progress of such a patient. Patients are at risk of developing micronutrient deficiency if they experience difficulty in swallowing and, as a consequence, alter their diet to one that may be deficient in one or more components. For example, fresh fruit and vegetables may be sacrificed in favour of highly processed foods, thus causing vitamin C deficiency. Another alternative that has to be considered in these patients is that because of the relentless, incurable, nature of their disease they may ingest excessive amounts of vitamin and trace element supplements in the vain attempt to halt the progression of their disease. A careful dietary assessment should be made in this man and, if suspected, vitamin or trace element deficiencies or excesses tested for biochemically.

Case history 42

Measuring the serum vitamin B₁₂ concentration is inappropriate in patients on parenteral treatment. A routine blood count is much more valuable. In a patient with pernicious anaemia feeling ‘run down’, other autoimmune diseases should be suspected. It would be reasonable to request thyroid function tests and glucose. The incidence of carcinoma of the stomach is increased among patients with pernicious anaemia and this diagnosis should also be borne in mind.

Case history 43

This patient has insufficient small bowel to enable him to be fed enterally. He will, therefore, require long-term parenteral nutrition. It is important that he is encouraged to take some oral fluids and nutrients to maintain the integrity of his remaining bowel.

The caloric and nitrogen requirements for restoration and maintenance of his skeletal muscle and body mass should be assessed. It is important to assess his baseline micronutrient status so that any deficiencies can be corrected. As he will receive the bulk of his nutrition parenterally in the future, his micronutrient status will need to be monitored. Once he is stable this should be formally checked at 6-monthly intervals along with his weight, skin-fold thickness and skeletal muscle mass.

Case history 44

In a patient such as this in ITU the biochemical measurements that are most frequently helpful are:

Serum urea and electrolytes to monitor renal function and serum potassium as he may become hyperkalaemic as a result of tissue damage.

Pulse oximetry to assess tissue oxygenation.

Blood gas analysis and plasma lactate, to detect and quantify acid–base disorders that may arise.

Serum muscle enzymes, such as CK may help detect a compartment syndrome or monitor rhabdomyolysis.

Case history 45

Recurrence or metastatic spread of the breast cancer would need to be excluded in this woman by imaging her liver and skeleton. Measurement of γGT and alkaline phosphatase isoenzyme studies may help to localize the source of the alkaline phosphatase. However, increased bone alkaline phosphatase does not necessarily signify bony metastases. In view of the history and symptoms, osteomalacia due to malnutrition or malabsorption may be the reason. If the patient has malabsorption or malnutrition she may have a macrocytic anaemia due to folate or B₁₂ deficiency and may be deficient in other vitamins or other micronutrients such as zinc. Malabsorption is often difficult to detect clinically and she should undergo tests for malabsorption such as faecal fat measurement.

Case history 46

This patient has the classic symptoms and signs of iron deficiency anaemia. The finding of a low serum ferritin with a low serum iron and per cent transferrin saturation are typical of this condition. However, if iron deficiency anaemia is suspected, the most important and usually the only investigation required is to demonstrate the presence of a hypochromic microcytic anaemia by examining the blood film, along with low haemoglobin.

Case history 47

The finding of a high liver copper concentration would indicate that the patient died from Wilson’s disease, which is an autosomal recessive disorder. The patient’s sister (and brothers, if any) should be screened for Wilson’s disease. Serum copper, caeruloplasmin and urinary copper excretion may indicate if she also has the disease. A liver biopsy may be indicated to confirm the diagnosis and allow treatment to be initiated. DNA analysis is becoming available to assist in the diagnosis. Due to the very large number of mutations DNA testing is only of value within families to detect affected members and identify carriers.

Case history 48

Erythromycin inhibits the metabolism of theophylline. Since the erythromycin treatment was still required, her theophylline was stopped for 2 days and restarted at a lower dose. Once the infection was clear she was recommenced on her original dose of theophylline.

Case history 49

These results would indicate that the man has taken an overdose of salicylate. The plasma salicylate of 4.6 mmol/L will contribute to his relatively high anion gap of 18 mmol/L. Salicylate poisoning is associated with a metabolic acidosis due to uncoupling of oxidative phosphorylation, and a respiratory alkalosis, due to direct stimulation by salicylate of the respiratory centre. The [H⁺] and PCO₂ indicate that the respiratory alkalosis is dominant at this stage.

In all cases of salicylate overdose the plasma paracetamol should also be measured as many proprietary analgesics contain aspirin and paracetamol. In the early stages of paracetamol poisoning, and when treatment is effective, patients will not display any specific signs or symptoms.

Case history 50

Many imported cosmetic agents contain lead. Not infrequently children will ingest these agents accidentally and may develop lead poisoning. It is, therefore, appropriate to measure the whole blood lead and erythrocyte protoporphyrin levels.

Case history 51

A high serum γGT is not diagnostic of alcohol abuse. γGT is induced by a number of enzyme-inducing agents such as phenytoin and phenobarbital, which this boy was taking. Currently, there is no definitive biochemical test to confirm alcohol abuse. However, the combination of an increased serum γGT and urate with a macrocytosis is strongly suggestive of alcohol abuse.

The alkaline phosphatase of 520 U/L is entirely appropriate for a teenager during his pubertal growth spurt. It should not be taken as indicative of liver disease.

Case history 52

Hypoglycaemia and diabetic ketoacidosis must be excluded. Blood glucose should be measured and blood or urine checked for ketones. Hypoglycaemia is more likely and should be treated with intravenous glucose. It is possible that the combination of hypoglycaemia, with or without alcohol intoxication, may have caused him to have an accident that could have resulted in a head injury causing his coma. Thus, in addition to monitoring his vital signs and grading his coma, it is essential to look for any superficial or neurological signs suggestive of head injury. It is essential that this be done even if he is demonstrated to be hypoglycaemic and rapidly recovers when given glucose, as the complications of a head injury such as subdural haematoma may not be immediately apparent.

Case history 53

This boy’s calculated osmolality is approximately 206 mmol/kg. Thus, the osmolal gap is approximately 76 mmol/kg. This has arisen because of his severe hyperlipidaemia, which causes pseudohyponatraemia. In severe hyperlipidaemia the increased lipids occupy a larger fraction of the plasma volume than usual, and the water a smaller fraction. Sodium is distributed in the water fraction only, and, in reality, these patients have a normal plasma sodium concentration. However, many of the instruments used to measure sodium take no account of this, and thus produce artefactually low sodium results.

Severe hypertriglyceridaemia in a child may be caused by a decrease in lipoprotein lipase activity. This may result from genetic defects in the enzyme itself or in the enzyme’s cofactor, apolipoprotein CII. Lipoprotein lipase is essential for the normal catabolism of chylomicrons and VLDL.

Two further notable points about very high triglycrides are that (a) they are a risk factor for developing acute pancreatitis, and (b) lipaemic samples cause analytical interference in measurement of various common analytes, including amylase (and thus may preclude laboratory confirmation of acute pancreatitis).

Case history 54

This man has diabetes mellitus, which is the most likely cause of his hyperlipidaemia. His γGT is high, which may be due to the presence of a fatty liver, a common finding in non-insulin-dependent diabetics on presentation. The high γGT may also be due to a high alcohol intake, which may contribute to his hypertension. However, the combination of diabetes mellitus with central obesity and hypertension would suggest insulin resistance or the so-called metabolic syndrome.

Details of his family history with respect to coronary heart disease should be obtained. Palmar or tuberous xanthomas should be looked for and, if present, would suggest type III hyperlipidaemia. His Apo E genotype should then be established.

This patient should be treated with dietary measures. Particular attention should be paid to his alcohol intake. Liver disease should be excluded as its presence would preclude the use of metformin, which would be an appropriate drug to treat his diabetes, or the use of statins or fibric acid derivatives to treat his hyperlipidaemia.

Case history 55

The concern would be that this patient has Cushing’s syndrome due to ectopic (malignant) production of ACTH. This is most frequently seen with carcinoma of the lung. As this disease is usually very aggressive, patients tend to develop florid metabolic features of the disease compared with the physical signs, which may be minimal. His serum urea and electrolytes indicate that he has developed profound hypokalaemic alkalosis and glucose intolerance. These can all be attributed to hypercortisolism. Cortisol will also cause muscle wasting that, combined with hypokalaemia, will lead to weakness. The nocturia and polyuria can cause profound potassium depletion.

Cushing’s syndrome should be confirmed by performing a dexamethasone suppression test. If the suspicion of malignant ectopic ACTH production is high, the low and high-dose suppression tests should be performed back to back. Measurement of urinary cortisol output will confirm cortisol over-production. His plasma ACTH concentration should be grossly elevated. In such cases, if carcinoma of the lung is demonstrated radiologically and/or by bronchoscopy, the diagnosis of ectopic ACTH production is made without necessarily confirming it biochemically. Conn’s syndrome and other conditions that may give rise to hypokalaemia with hypernatraemia are much rarer.

Case history 56

Though he is not clinically jaundiced the high alkaline phosphatase and γGT with modest increases in the AST and ALT would suggest cholestasis. This may be due to liver cirrhosis or malignant disease affecting the liver, both of which would be likely diagnoses in this case. Liver congestion resulting from cardiac failure would explain the clinical findings, but the biochemistry of congestion is classically dominated by raised transaminases; cholestasis is usually only a minor feature. This is the opposite of the picture here.

An AFP level may be helpful as it is a good tumour marker for hepatocellular carcinoma, which is also a likely diagnosis in this case. The most common predisposing factors to the development of hepatocellular carcinoma are alcoholic cirrhosis in Western countries and hepatitis B in the developing world.

Case history 57

The patient’s plasma PTH should be measured and, if increased, a diagnosis of primary hyperparathyroidism can be made. However, hyperparathyroidism with a serum calcium of 2.8 mmol/L is usually asymptomatic and thus another cause for his hypertension, headaches and anxiety should be sought. If the symptoms were episodic this would suggest the possibility of a phaeochromocytoma, which is associated with hyperparathyroidism in families with MEN. The patient should have his urinary catecholamines measured and, if the diagnosis is made, it is important that other members of his family be screened for hyperparathyroidism and phaeochromocytoma.

Case history 58

Acute severe pain in the metatarsophalangeal joint is the classic presentation of gout. The serum urate level is usually high in gout, but only a minority of patients with hyperuricaemia develop gout and frequently patients with acute gout may have a normal serum urate level. The presence of fever would be compatible with septic arthritis. The joint should be aspirated and, in addition to looking for urate crystals that would confirm a diagnosis of gout, some of the aspirate should be sent for microbiological studies to exclude the possibility of infection.

Case history 59

The large increase in the CK and LDH relative to the AST and ALT would indicate that muscle is the major tissue contributing to the increase in serum enzyme activities. However, muscle cells contain only small amount of ALT; AST and LDH are found in muscle, liver and erythrocytes. Thus, the tissues that could have contributed to the serum enzyme activities include muscle (either skeletal or cardiac), the liver or erythrocytes.

By measuring troponin T or I one can determine whether or not cardiac muscle is involved. If the liver is involved then the serum γGT should be increased as this is one of the most sensitive indicators of liver disease. Although LDH isoenzyme studies may help to identify erythrocyte damage as a possible source of LDH and AST, it may be more useful to look for other evidence of haemolysis, e.g reticulocytosis and absent or low haptoglobin.

Case history 60

Elderly people living on their own frequently have an inadequate diet. This is particularly true of men if they are unused to cooking for themselves. This patient may have a number of micronutrient deficiencies but, acutely, the most important would be possible thiamine deficiency. This can be detected by demonstrating an increase in the percentage activation of erythrocyte transketolase in vitro by the addition of thiamine or the measurement of thiamine pyrophosphate in erythrocytes. These investigations are often unavailable in the acute situation and patients are usually treated empirically with multivitamin preparations. When micronutrient deficiency is suspected, the diagnosis can only be confirmed if the appropriate samples are collected before the patient is given supplements.

Case history 61

This woman should have an amniocentesis performed with bilirubin being measured in her amniotic fluid. In Rhesus incompatibility the amniotic fluid bilirubin concentration will rise because of the destruction of fetal red cells by maternal antibodies.

Case history 62

Pre-eclampsia is the most likely diagnosis. The most appropriate side room test to perform would be to test for albuminuria. Biochemical investigations that should be performed on this woman are:

Serum urate, as this is a sensitive indicator for pre-eclampsia.

Serum urea and electrolytes should be measured as she may be developing renal failure.

Serum albumin and liver function tests should be performed to detect liver disease.

Case history 63

No other investigations should be performed, but the parents should be reassured that their daughter does not have congenital hypothyroidism.

Over 99% of all 6-day-old children will have a TSH of <10 mU/L while the majority of patients with congenital hypothyroidism will have a TSH >100 mU/L. Babies with a blood TSH between 15 and 40 mU/L on their first test are considered to have an equivocal result. If in a second sample a normal result is obtained, as is usually the case, no further investigation need be made.

Case history 64

This baby’s blood gas status should be assessed as she is at risk of developing the respiratory distress syndrome. In view of her maternal history, weight and gestational age, she may be hypoglycaemic and her blood glucose should be measured. Hypocalcaemia is another possibility that should be considered, so her serum calcium should be measured.

The total blood volume in neonates is small and could be less than 100 mL in this baby. It is, therefore, very important to collect the minimum blood from neonates as they can become anaemic if a large number of investigations are performed.

Clinical Biochemistry An Illustrated Colour Text-5E

Recent Posts

Meta

Categories

Search Engine

Case history comments

Case history comments

Share this:

Related

Related posts: