Acute back pain in a 75-year-old man

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Problem 22 Acute back pain in a 75-year-old man

You are asked to see a 75-year-old retired electrician who has been brought into the emergency department with an 18-hour history of increasing back pain. He tells you that the pain came on gradually and now goes down into his left groin and thigh. The pain is constant, getting worse. He has never had this pain before. He does not think the pain was precipitated by anything and nothing seems to ease it. In particular, there is no history of trauma, and walking or exertion do not affect it. There are no other associated symptoms.

Eight months ago he suffered a myocardial infarction and since that time has suffered with moderate angina on effort. He takes isosorbide dinitrate 10 mg three times a day for the angina and uses nitrate skin patches at night. He used to smoke 20 cigarettes a day, but ceased after his heart attack. He drinks 20 g of alcohol per day at the weekends. He suffers occasional episodes of indigestion for which he takes an over-the-counter antacid preparation.

The review of systems is otherwise unremarkable apart from symptoms of increasing bladder neck outflow obstruction, which have been worse over the last 2 years. He gets up twice every night to void and says he feels that he can never empty his bladder properly. He has not passed urine since the pain started.

Q.1

What diagnoses go through your mind?

On examination he is thin and in pain. His blood pressure is 140/90 mmHg and he has a regular pulse rate of 100 bpm. His jugular venous pressure is not elevated and his apex beat is displaced 2 cm lateral to the mid-clavicular line and is felt in the fifth interspace. Both heart sounds are normal with no added sounds. His chest is resonant and breath sounds are vesicular. He has a tender, pulsatile mass in the abdomen which feels about 6–7 cm in diameter and is situated at the level of the umbilicus. There is dullness to percussion in the suprapubic region extending four fingerbreadths above the pubis. Both femoral pulses are of good volume and pedal pulses are palpable. His legs are neurologically normal and the straight leg raise and sciatic stretch tests are negative. The patient’s previous X-rays are available.

The patient recently had an abdominal ultrasound for his urinary frequency (Figures 22.1 and 22.2).

Figure 22.1

Figure 22.2

Q.2

What does the investigation show?

The ultrasound findings confirm your clinical suspicions.

Q.3

What is your next action?

Q.4

What further investigations may be indicated?

As this patient is haemodynamically stable, a further investigation is performed expeditiously. Two of the images are shown (Figures 22.3 and 22.4).

Figure 22.3

Figure 22.4

Q.5

What type of images are these and what do they show? How do these findings affect your management?

The patient and his family are informed of the diagnosis and the likely outcome if surgery is not undertaken promptly. The aneurysm is in imminent danger of rupture, with a subsequent high mortality. Surgery also has its risks, particularly in this patient with known cardiac disease.

The cardiologists and anaesthesiologists are asked to review the patient, and prepare him for emergency surgery. At surgery, the aneurysm is repaired using a dacron tube graft. Following the procedure he is transferred to the intensive care unit.

Q.6

What complications may follow an aortic aneurysm repair?

The patient makes an uneventful recovery and is home 10 days after the procedure.

Answers

A.1 Acute pain in the back, radiating to the groin, in an elderly male with known atheromatous disease must make you consider a leaking or stretching abdominal aortic aneurysm. This is the diagnosis that needs to be excluded. Other conditions include:

• Aortic dissection.

• Acute pancreatitis.

• Ureteric colic.

• Urinary retention.

This is unlikely to be a musculoskeletal problem (e.g. herniated disc), as the pain is not aggravated by movement.

A.2 The ultrasound shows a large fusiform abdominal aortic aneurysm. The image in Figure 22.1 shows the aneurysm in transverse section and in Figure 22.2 the aorta in longitudinal view. Some thrombus is shown in the posterior wall. The measurement of aneurysm size is taken on the transverse image and is the maximum anteroposterior or transverse diameter. The length of the aneurysm is not important from a management point of view.

A.3 This man has an abdominal aortic aneurysm, which is symptomatic and may now be leaking or about to leak. This is a vascular emergency. Your priority is to insert a wide-bore intravenous catheter, collect blood for electrolytes, full blood count, basic coagulation studies (APTT and INR) and group and match blood. You must alert the vascular surgeons immediately. You must also attach a cardiac monitor and insert a urinary catheter to monitor urine output, and notify the patient’s relatives.

A.4 The need for further investigations will hinge on whether the patient is haemodynamically stable. If not stable, further investigations will only delay definitive management. In that case, the patient should go directly to the operating theatre.

As the patient is haemodynamically stable, the surgeons may request a CT scan of the aorta to assess the size of the aneurysm, its relationship to the renal arteries, whether it has leaked and to exclude any other cause of intra-abdominal pain.

A.5 Figure 22.3 shows a standard transverse cut through the aneurysm sac. Contrast has been administered and the non-enhancing contents of the aneurysm sac represent laminated thrombus. It is these images which provide the surgeon with vital information regarding the presence or absence of a leak. This shows a 5.8 cm abdominal aortic aneurysm which had not leaked. The pain is presumably due to expansion and stretching of the aneurysm.

Figure 22.4 is a spiral CT angiogram reconstruction. The reconstruction gives the surgeon useful information regarding patency/stenoses of renal and iliac arteries, vessel tortuosity and relationship of the aneurysm to the renal arteries. The renal arteries are patent and the iliac vessels are not aneurysmal.

The transverse cuts give the essential diagnostic information regarding size of the aneurysm sac and the presence or absence of leaking blood. The laminated thrombus in the sac does not show up on CTA reconstructions. The spiral CT reconstruction is essential in either the elective situation or in urgent repair when the patient is haemodynamically stable.

A.6 The majority of the mortality (2–10%) and morbidity associated with elective abdominal aortic aneurysm repair is due to pre-existing cardiac disease. The risk of a peri- or early postoperative myocardial infarction in this man will be high.

Other possible complications include:

• Cerebrovascular event.

• Acute thrombotic/embolic events leading to:

– renal failure

– bowel infarction

– acute lower limb ischaemia.

• Sepsis – chest or wound.

• Graft infection.

Revision Points

Abdominal Aortic Aneurysms (AAA)

Incidence

• 5% of males over 65 years of age.

• Less common in women.

• Occur in 10–15% of claudicants.

Risk Factors

• Smoking.

• Hypertension.

• Hyperlipidaemia.

• Genetic predisposition.

Note: diabetes is not a risk factor.

Pathology

• Degenerative process involving all layers of aortic wall.

• Appears to be caused by increased activity of matrix metalloproteinases (extracellular matrix-degrading enzymes which break down collagen and elastin in the aortic wall). These enzymes seem to be activated by aortic endothelial injury caused by smoking, hypertension or hyperlipidaemia: i.e. aneurysms are not caused by atherosclerosis, although atherosclerosis frequently co-exists.

Clinical Features

• Most frequently asymptomatic.

• May present with abdominal, back or loin to groin pain (if stretching, leaking or ruptured).

• Collapse or cardiac arrest may occur in acute rupture.

Natural History

• Aneurysms less than 5–5.5 cm in diameter rarely rupture (1–2% per year).

• Rupture rate increases exponentially with increasing size over 5.5 cm.

Management

• AAA less than 5 cm in diameter should be treated with aggressive control of risk factors and 6-monthly ultrasound surveillance, unless there is rapid increase in size or development of symptoms, e.g. abdominal or back pain.

• AAA over 5 cm can be considered for repair if risks of surgery (mainly cardiorespiratory) are less than risk of rupture.

• Open surgical repair is most durable technique for fixing AAA.

• Endoluminal stent graft repair is frequently used in anatomically suitable cases. This procedure is associated with lower morbidity and mortality but requires lifelong surveillance with re-intervention rates of 5–10% per year to maintain exclusion of the aneurysm sac.

Issues to Consider

• How might a thoracic aortic aneurysm present?

• How would you diagnose and manage aortic dissection?

• Why do symptomatic patients develop groin and testicular pain?

Further Information

Symons N.R, Gibbs R.G. The management of abdominal aortic aneurysms. British Journal of Hospital Medicine. 2009;70:566-571. A review of current management

United Kingdom Small Aneurysm Trial Participants. Long-term outcomes of immediate repair compared with surveillance of small abdominal aortic aneurysms. New England Journal of Medicine, 346. 2002:1445-1452. www.NEJM.com.

www.scvir.org/patient/aaa/. A website from the Society for Cardiovascular and Interventional Radiology. Patient directed but with good information about endoluminal treatments