Renal circulatory insufficiency

There will usually be a recent history of a condition which causes renal hypoperfusion. This may include haemorrhage, burns or dehydration, e.g. from vomiting, diarrhoea or acute pancreatitis.

Renal causes

In the absence of adequate resuscitation, shock will proceed to cause damage to the tubules, resulting in acute tubular necrosis. Acute cortical necrosis may arise as a result of antepartum haemorrhage, eclampsia or septic abortion. It may also follow insults similar to those that cause acute tubular necrosis. Vascular lesions may also lead to acute renal failure; these include renal vein thrombosis, renal artery stenosis and intravascular coagulation occurring in haemolytic uraemic syndrome. Other forms of acute renal failure usually present with swelling of the eyelids, ascites and peripheral oedema. Later, there may be vomiting, confusion, bruising, gastrointestinal bleeding and eventually fitting and coma. Volume overload may result in pulmonary oedema. With acute interstitial nephritis, there may be a history of drug ingestion, e.g. antibiotics, NSAIDs or diuretics, or there may be a history of infection. Nephrotoxins may cause acute renal failure and among the drugs implicated are the aminoglycosides, amphotericin and radiographic contrast media. Organic solvents, particularly carbon tetrachloride used in carpet cleaning, may be responsible. Paraquat, snake bites and mushrooms may also cause acute renal failure.

Post-renal

Often the patient will present with complete anuria. This may occur if there is ureteric damage following surgery or a stone impacted in the ureter of a solitary functioning kidney. The patient may have a history of calculous disease or may have recently suffered an attack of ureteric colic. There may be a history of pelvic tumour or symptoms of prostatic hypertrophy, e.g. difficulty in starting and a poor stream. Retroperitoneal fibrosis often develops insidiously.

Others

Oliguria may follow a mismatched transfusion, due to haemoglobinuria, or crush injuries, due to myoglobinuria. The history will usually be obvious.

Anuria

Before diagnosing anuria, make sure that the patient does not have a palpable bladder (if he or she is not catheterised) and is not therefore in acute retention, or, if the patient is catheterised, that the catheter is not blocked. As indicated above, anuria is more likely to be a symptom of an obstructive lesion rather than one of renal hypoperfusion or an intrinsic renal lesion.

General

If the patient has a catheter in situ, make sure that it is not blocked. If the patient does not have a catheter in situ, palpate the lower abdomen for a distended bladder associated with acute retention. Palpate the abdomen to exclude swelling of the kidneys and perform a rectal examination to exclude prostatic hypertrophy.

Specific

All causes of oliguria are likely to have some common features on examination. The patient will be dyspnoeic due to pulmonary oedema and will either have sacral oedema (if confined to bed) or ankle oedema (if ambulant). There may be confusion, drowsiness, fitting or coma. Hypertension and arrhythmias may be present. The patient will be nauseated, may be vomiting, have hiccups and there may be evidence of gastrointestinal haemorrhage. Spontaneous bruising may eventually occur.

■ FBC, ESR
Hb ↓ anaemia, renal failure, haemorrhage. WCC ↑ infection. ESR ↑ some causes of glomerulonephritis.

■ U&Es
Urea ↑, creatinine ↑ in renal and post-renal causes. These may rise in renal hypoperfusion if not adequately treated.

■ ECG
Arrhythmias. Associated with electrolyte imbalance, e.g. hyperkalaemia.

■ CXR
Pulmonary oedema. Cardiomegaly.

■ ABGs
Metabolic acidosis.

■ MSU
Red cells, casts and protein in intrinsic renal disease. Hb-positive but no red blood cells suggests myoglobinuria or haemoglobinuria.

■ Urine electrolytes
See Table below.

■ Urine osmolality
See Table below.

■ US
Obstructive lesion.

■ Cystoscopy and ureteric catheterisation with retrograde pyelography
Cause of obstruction, possible relief of obstruction.

■ Antegrade pyelography
Cause of obstruction. Relief of obstruction.

■ DMSA scan
Renal function. Infarction. Absent outline of kidney.