Indication	Advantage of CT
Pancreatitis	Demonstrates pancreatic necrosis
Aortic aneurysm	CT scanning is the only reliable way to exclude aortic rupture (ultrasound detects aneurysms but does not exclude rupture)
Severe or non-resolving diverticulitis	Allows differentiation between localised perforation of diverticulum, diverticular abscess, diverticular mass
Large bowel obstruction	Avoids need for water-soluble contrast enema. Usually accurately demonstrates level of obstruction and cause
Small bowel obstruction with no hernia or scars	May detect the cause of the obstruction preoperatively
Suspicion of malignancy	Acute abdominal pain is common in advanced malignancy. CT scanning may confirm extensive metastatic disease, avoiding laparotomy when palliative care is more appropriate
Peritonitis in absence of gas on AXR	CT scanning is very sensitive for small pockets of free gas after perforation of a viscus
Acute abdomen	Standard in many hospitals

Ultrasound

Ultrasound reliably detects free fluid, gallstones, intrahepatic duct dilatation and aortic aneurysm. It is less useful for looking at bowel (sound does not penetrate gas-filled structures). It is operator dependent and picture quality is affected by body habitus and presence of bowel gas. Pelvic ultrasound is useful for detecting gynaecological disorders when diagnosing appendicitis in the female.

Contrast studies

Contrast studies including barium meal, follow-through, water-soluble contrast enema and intravenous urography may each be useful in selected settings.

Patterns of abdominal pain

Appendicitis

Pain is initially central, then localises to the right iliac fossa with guarding and rebound tenderness (Fig. 5.1).

Figure 5.1 Symptoms, signs and differential diagnosis of appendicitis. NSAP, non-specific abdominal pain.

Aetiology and pathology

Appendicitis is the commonest cause of the acute abdomen in the United Kingdom. It occurs when there is an obstruction of the lumen either by faecolith or foreign body or enlargement of the lymphoid follicles in its wall. It may affect any age but is rare in the extremes of life.

Rare causes of appendicitis include carcinoma of the caecum, carcinoid tumour or obstructing fibrous bands. A severely inflamed appendix may be walled off by omentum (an appendix mass) which will eventually contain pus (an appendix abscess). Untreated, the condition threatens life in the very young and elderly, mainly because the diagnosis is difficult.

The appendix may be in a number of different positions in relation to the caecum: medial; medial and below; extending over the pelvic brim; retrocaecal; or retroileal.

Clinical features

Symptoms

The pain starts as central abdominal associated with anorexia, nausea and occasional episodes of vomiting. As the organ becomes inflamed, local peritoneal irritation causes more severe right iliac fossa pain. If the appendix ruptures, generalised peritonitis results and the pain becomes spread across the whole abdomen.

If the appendix is lying close to the ureter/bladder then irritative urinary symptoms may result.

Signs

A coated tongue and fetor oris accompanied by mild pyrexia are characteristic. Local tenderness and guarding at McBurney’s point (the junction of the middle and outer third of the line which joins the umbilicus to the anterior superior iliac spine) is present. These signs may vary, particularly when the appendix is in the retrocaecal position. Pressure applied to the left iliac fossa causes increased pain in the right lower quadrant (Rovsing’s sign) but this is unreliable. Pelvic examination may be helpful in an attempt to localise the site of maximum tenderness.

Investigations

Appendicitis remains mainly a clinical diagnosis but investigations help reduce unnecessary operations to remove normal appendices. This is especially so in females where UTI, salpingitis, ectopic pregnancy and ovarian cysts may mimic appendicitis.

• The WBC is usually raised

• AXR is of no value in appendicitis

• The urine often contains leucocytes, but no organisms

• Pregnancy test in females is mandatory to exclude ectopic pregnancy

• Abdominal/pelvic ultrasound may not diagnose appendicitis but usefully rules out ovarian pathology

• In the older patient, CT detects caecal carcinoma and diverticulitis, and reduces normal appendix removals – becoming standard

• Diagnostic laparoscopy in young females is accurate at identifying gynaecological conditions which mimic appendicitis.

Scoring systems are variably used (e.g. the Alvarado score) but are no substitute for clinical experience and regular re-evaluation of the patient, and may increase the use of cross-sectional imaging.

Treatment (see Box 5.3)

Once the diagnosis has been made, appendicectomy is required. This may be done through a small, transverse incision of the right iliac fossa or laparoscopically. Prophylactic antibiotics reduce the incidence of wound or port site infection.

Box 5.3 History of modern surgery

Appendicitis

Described for centuries as ‘the iliac passion’ the successful removal of an acutely inflamed appendix was first reported in 1887 by the American Surgeon Thomas Morton, who (successfully) resorted to laparotomy only after the failure of poultices, enemas and leeches to produce a cure.

An appendix mass may be managed non-operatively with parenteral fluids, antibiotics and frequent clinical re-assessment and imaging. The majority of the masses resolve and elective appendicectomy may be undertaken some weeks later. In the elderly, a preliminary barium enema or colonoscopy is advised to exclude carcinoma.

Appendix abscesses may be drained percutaneously by ultrasound with subsequent delayed operation 6 weeks later.

Appendicitis in pregnancy

Pain and tenderness are higher because of the displacement of the appendix by the enlarging uterus. Prompt assessment and intervention are essential. The risk of abortion in the first trimester is considerably higher if treatment is delayed until perforation occurs.

Intestinal obstruction (Fig. 5.2)

Classification and causes

Bowel obstruction may be due to mechanical obstruction or failure of peristalsis. The main clinical issue is to determine whether the obstruction affects the small bowel or the colon, since the causes and treatments are different.

Figure 5.2 Bowel obstruction.

The causes of mechanical obstruction are summarised in Box 5.4. In general, the commonest causes of small bowel obstruction are adhesions or hernia (Table 5.2), and those of large bowel obstruction are colon cancer or diverticular mass.

Table 5.2 Causes of small bowel obstruction

Cause	Examination pointers	Requirement for surgery
Adhesions from previous surgery	Look for the abdominal scar (the surgery may have been many years ago)	Likely to resolve with non-operative treatment
Strangulated hernia	Examine hernial orifices carefully: it is easy to miss a small femoral hernia in an obese patient	Unless the hernia can be reduced easily, surgery will be required

Clinical features

The features of bowel obstruction are colicky abdominal pain, vomiting, abdominal distension and constipation.

If the colic is in the lower abdomen it is more likely to be due to colon obstruction. Vomiting follows the pain. For high obstructions, vomiting is more profuse and occurs earlier. In colon obstruction the vomiting occurs much later if at all, especially if the ileocaecal valve remains competent. Initially, food contents are vomited but later the vomit becomes faeculent (brown and foul smelling). Distension is usually evident and more marked the more distal the obstruction. Constipation is absolute (i.e. no faeces or flatus).

The physical findings include dehydration, abdominal distension and sometimes visible peristalsis. The cause of the obstruction may be evident (e.g. scars from previous surgery, a tender irreducible hernia, an abdominal mass). Percussion produces a tympanic note and auscultation high-pitched tinkling bowel sounds.

If the obstruction is advanced there may be signs of bowel strangulation (worsening constant pain, toxic patient, tachycardia and hypotension, pyrexia). Rectal examination must ALWAYS be performed in bowel obstruction. The rectum will be empty unless the cause of the problem is impacted faeces. A pelvic mass may be palpable.

Investigations

Plain abdominal X-rays confirm the diagnosis and distinguish small from large bowel obstruction.

AXR features of small bowel obstruction:

• distended loops of small bowel (over 3 cm)

• no gas is seen in the colon or rectum.

AXR features of large bowel obstruction:

• distended colon (over 5 cm) proximal to the obstructing lesion, collapsed colon distally; this is known as the ‘cut-off’ sign

• distended small bowel may also be seen if the ileocaecal valve is incompetent.

CT scanning is excellent at confirming diagnosis and identifying the level of the obstruction – use it often.

Small bowel obstruction

Adhesions and hernias are the commonest causes of small bowel obstruction. If there is no abdominal scar or irreducible hernia, consider Crohn’s disease, small bowel lymphoma, caecal carcinoma obstructing the ileocaecal valve and internal hernia.

Treatment requires IV fluid replacement and nasogastric decompression (’drip and suck’). Patients with bowel obstruction may be severely dehydrated and may require large volumes of fluid resuscitation (use 0.9% saline, NOT dextrose). Catheterise the bladder, monitor hourly urine output and watch U&E closely. A CVP line may be needed in the elderly.

Most cases of adhesion obstruction resolve with nonoperative management. Surgery is required if there is evidence of bowel strangulation: watch carefully for clinical deterioration, pyrexia, development of localised tenderness or peritonism and rising WBC or acidosis.

Large bowel obstruction

When a diagnosis of large bowel obstruction is suspected on AXR, the next step is to exclude pseudo-obstruction (Box 5.5) and to determine the site of the obstructing lesion. This requires either water-soluble contrast enema or CT scan.

Box 5.5 Causes of large bowel obstruction

Pseudo-obstruction

Mechanical obstruction:

Carcinoma of the colon

Diverticular stricture

Diverticular abscess/mass

Crohn’s disease

Faecal impaction

Pseudo-obstruction

Pseudo-obstruction has the same clinical features as mechanical colon obstruction but there is no mechanical obstructing lesion. The problem results from failure of peristalsis. The condition is commonly seen in elderly inpatients and is associated with abnormal electrolytes, diuretics, analgesics and antidepressant or antipsychotic therapy. AXR shows dilated colon from caecum to rectum. The rectum is distended with gas or liquid faeces. Colonoscopic decompression may provide relief. Correction of the underlying metabolic abnormality is the priority.

Neostigmine infusion may be used for refractory cases but ECG monitoring is essential as the drug may induce cardiac arrhythmias.

Pseudo-obstruction may occasionally cause caecal perforation, which requires laparotomy, but most cases resolve with non-operative therapy.

Treatment of large bowel obstruction

Treatment of large bowel obstruction depends on the underlying cause. Lesions causing mechanical obstruction require laparotomy and resection of the affected colon. The bowel may be restored in continuity immediately, or a temporary colostomy may be performed.

Acute pancreatitis (see p. 139)

See Figure 5.3.

Figure 5.3 Acute pancreatitis.

Diverticulitis (see p. 152)

See Figure 5.4.

Figure 5.4 Diverticulitis.

Perforated viscus

See Figure 5.5.

Figure 5.5 Perforated viscus.

Constipated elderly patient (a dangerous diagnosis)

See Figure 5.6.

Figure 5.6 Constipated elderly patient.

Ureteric colic (see p. 249)

See Figure 5.7.

Figure 5.7 Ureteric colic.

Biliary colic (see p. 135)

See Figure 5.8.

Figure 5.8 Biliary colic. CBD, common bile duct.

Ruptured abdominal aortic aneurysm (see p. 207)

See Figure 5.9.

Figure 5.9 Ruptured abdominal aortic aneurysm.

Painful testicle

Epididymo-orchitis

In boys, a painful testicle must be assumed to be due to torsion (see below). After puberty, epididymo-orchitis is more likely. In young men this is usually due to sexually transmitted infection, whereas in older men secondary infection due to bladder outflow obstruction is the commonest cause.

Investigation

• Urine culture

• Scrotal ultrasound (exclude underlying testicular tumour or abscess).

Treatment

Analgesia and antibiotics.

Testicular torsion

Torsion of the testicle is a surgical emergency, since the twisting of the spermatic cord cuts off the blood supply to the testes, which will infarct within 6 hours. Torsion occurs in boys at any age and is rare after puberty. There is severe pain in the testicle and iliac fossa. Vomiting is common. The testicle is extremely tender, swollen and drawn up.

The differential diagnosis includes epididymo-orchitis, torted hydatid of Morgagni (appendix testes) and idiopathic scrotal oedema. Immediate exploration of the scrotum is required since no investigation will reliably distinguish torsion from the other causes. Consent must be obtained for orchidectomy in case the testicle is non-viable. The opposite testicle is fixed at the same operation to prevent torsion on the other side.

Urinary retention

Acute urinary retention

Patients are invariably male, usually over 50. Symptoms are suprapubic pain of sudden onset, with inability to pass urine. The patient is distressed and the bladder is tender and palpable.

The commonest causes are benign prostatic hypertrophy, prostate cancer, bladder cancer, urethral stricture and urinary infection causing prostatic and urethral inflammation and constipation. About half of patients have a history of obstructive urinary symptoms due to prostate hypertrophy. There is often a precipitating event such as cystoscopy, surgery elsewhere on the body (especially groin hernia) and overdistension of the bladder (e.g. on a coach journey).

Treatment requires catheterisation of the bladder, usually per urethra. If urethral catheterisation is unsuccessful (or contraindicated such as in pelvic trauma) then suprapubic catheterisation can be attempted by more specialist practitioners (risk of bowel or vascular injury).

After catheterisation the cause of the retention must be established. Examine the prostate (small/large/hard/irregular). Check FBC, U&E, PSA (though the PSA is always raised just after catheterisation) and send urine for culture and cytology. Renal ultrasound is necessary if there is renal impairment.

A trial without catheter (a ‘TWOC’) is usually attempted after an interval of up to two weeks (often in the urology outpatient clinic), the patient having been given a course of medication aimed at reducing the degree of prostatic hypertrophy. If this is unsuccessful, prostatectomy is usually offered (see p. 252).

Chronic urinary retention

Chronic retention commonly presents as a non-specific illness and there may be no pain from the bladder at all, which is lax and grossly distended (up to several litres) compared to acute retention. The patient may frequently pass small volumes of urine and is often incontinent (overflow incontinence).

After catheterisation for chronic retention, there may be hypotension (a vagal response) and haematuria due to bleeding from submucosal veins inside the bladder. Decompressing the bladder in stages may help but evidence suggests the severity of damage is correlated to the degree of distension.

Chronic retention is often associated with renal impairment and after bladder decompression severe polyuria may cause hypotension and collapse. Hourly urine measurements must be taken and if polyuria occurs, a safe regimen is to replace urine output with an equal volume of IV 0.9% saline until equilibrium is restored.

Acute limb ischaemia

Lower limb ischaemia

Presentation

Presentation of acute limb ischaemia is characterised by ‘the 6 Ps’: pain, pallor, paraesthesia, paralysis, pulselessness and perishing cold. The Doppler signal is often undetectable or severely diminished at the ankle (i.e. the ankle-brachial pressure index (ABPI) is at or close to zero).

Untreated, within a few hours such a limb will become mottled with fixed staining of the skin, the paralysis will be complete and the muscles will become tense, tender and swollen. Once these features have developed the limb is non-salvageable and amputation is necessary to save the life of the patient.

Management

Time is of the essence. Inform a senior as soon as a patient with acute limb ischaemia is expected. Patients with acutely ischaemic limbs are in great pain and often in poor health, hypoxic, dehydrated with failing heart and kidneys. Treating these conditions appropriately often brings about a marked improvement in the affected limb without any specific vascular intervention, simply by improving circulation of well-oxygenated blood.

Immediate action to be taken is outlined in Box 5.6. The next priority is to obtain imaging to determine the cause of the ischaemia and to plan treatment. Duplex ultrasound, magnetic resonance angiography, CT angiography and digital subtraction angiography are all useful; the choice of modality depends on the local facilities available.

Box 5.6 Immediate actions to be taken in the event of acute lower limb ischaemia

Oxygen: at least 24–28% via face mask

Take blood for FBC, baseline coagulation studies, G&S, U&E, glucose

Do CXR and ECG

Heparin: give a bolus of 5000 units IV then infuse 1000 units per hour to maintain the APTR at between 2 and 3 (monitor APTR every 6–8 hours and titrate heparin dose)

Rehydration: set up intravenous infusion and catheterise the bladder to monitor fluid balance

Analgesia: morphine 5–10 mg IV with 10 mg metoclopramide

Treat specific co-morbid conditions, e.g. fast atrial fibrillation, cardiac failure or pneumonia

Many patients present with so-called acute subcritical limb ischaemia. In these patients the pain is of recent onset (less than 2 weeks) but there is no paralysis and the sensory loss is mild. There may even be a weak audible Doppler signal at the ankle.

Treatment options include:

• palliative care

• primary amputation

• urgent surgery (embolectomy or bypass)

• thrombolysis

• endovascular therapy (suction thrombectomy, angioplasty with or without stenting).

Irreversible limb ischaemia requires amputation or palliative care. The acute white bloodless leg needs immediate intervention to save the limb. The distinction between thrombosis and embolism may not be obvious. Pointers towards embolism include no past history of claudication, normal pulses in the opposite leg and a likely embolic source, usually atrial fibrillation. In these patients the best approach is urgent exploration of the groin with balloon embolectomy of the femoral arteries and on-table angiography.

Thrombolysis is achieved by inserting an arterial catheter into the thrombosed artery and infusing the thrombolytic agent (usually tissue plasminogen activator: TPA). This may unblock small and large arteries and reveal the lesion that led to the occlusion (e.g. an arterial stenosis or popliteal aneurysm). The technique is less invasive than surgery but has a high incidence of bleeding complications and stroke, particularly in those over 80 years of age.

Upper limb ischaemia

In contrast to the leg, upper limb ischaemia is usually due to embolisation from the heart. Brachial embolectomy may be needed but in many cases heparinisation and hydration are sufficient. The underlying cause must be sought (echocardiography, CXR for cervical rib, upper limb duplex scan).

Perianal abscess (see p. 165, 360)

Perianal abscess is the commonest of a number of painful anal conditions which present on the general surgical take (Table 5.3). Examination under anaesthetic is usually required so that sigmoidoscopy (exclude Crohn’s disease) and adequate drainage of the abscess may be performed.

Table 5.3 Acutely painful anal conditions

Condition	Treatment	Page reference
Perianal abscess	Examination under anaesthesia including sigmoidoscopy, incision and drainage, culture swab, histology of abscess roof	See p. 165, 360
Anal fissure	Trial of medical treatment (glyceryl trinitrate or diltiazem ointment) and/or examination under anaesthesia, injection of botox to internal anal sphincter or lateral sphincterotomy	See p. 164
Thrombosed haemorrhoid	Usually conservative, analgesics, ice and metronidazole, occasionally emergency haemorrhoidectomy	See p. 162
Perianal haematoma	Evacuation under local anaesthetic provides immediate relief	See p. 164