Somatic pain

The parietal peritoneum covers the anterior and posterior abdominal walls, the undersurface of the diaphragm and the pelvic cavity. It develops from the somato-pleural layer of the lateral plate mesoderm and its nerve supply is therefore derived from somatic nerves supplying the abdominal wall musculature and the skin (T5–L2). The exception to this is the diaphragmatic portion, which is supplied centrally by afferent nerves in the phrenic nerve (C3–C5), and peripherally in the lower six intercostal and subcostal nerves.

The parietal peritoneum is sensitive to mechanical, thermal or chemical stimulation, and cannot be handled, cut or cauterized painlessly. As a result of its innervation, when the parietal peritoneum is irritated, there is reflex contraction of the corresponding segmental area of muscle, causing rigidity of the abdominal wall (guarding) and hyperaesthesia of the overlying skin.

When the diaphragmatic portion of the parietal peritoneum is irritated peripherally, there will be pain, tenderness and rigidity in the distribution of the lower spinal nerves, but when it is irritated centrally, pain is referred to the cutaneous distribution of C3, 4 and 5 (i.e. the shoulder area, Fig. 12.1). Somatic pain is classically described as sharp or knife-like in nature, and is usually well localized to the affected area.

Fig. 12.1 The shared sensory innervation of the shoulder and diaphragm.

Visceral pain

The visceral peritoneum forms a partial or complete investment of the intra-abdominal viscera. It is derived from the splanchno-pleural layer of the lateral plate mesoderm, and shares its nerve supply with the viscera (i.e. the autonomic nerves). Visceral pain is mediated through the sympathetic branches of the autonomic nervous system, with afferent nerves joining the pre-sacral and splanchnic nerves, which eventually join thoracic (T6–T12) and lumbar (L1–L2) segments of the spinal cord. The visceral peritoneum and the viscera are insensitive to mechanical, thermal or chemical stimulation, and can therefore be handled, cut or cauterized painlessly. However, they are sensitive to tension, whether due to overdistension or traction on mesenteries, visceral muscle spasm and ischaemia.

Visceral pain is typically described as dull and deep-seated. It is usually localized vaguely to the area occupied by the viscus during development, and is referred to the overlying skin of the abdominal wall according to the dermatome level with the sympathetic supply, as mentioned above. Therefore, pain arising from the intestine and its outgrowths (the liver, biliary system and pancreas) is usually felt in the midline. Irritation of foregut structures (the lower oesophagus to the second part of the duodenum) is usually felt in the epigastric area. Pain from midgut structures (the second part of the duodenum to the splenic flexure) is felt around the umbilicus. Pain from hindgut structures (the splenic flexure to the rectum) is felt in the hypogastrium.

Although the division of abdominal pain into visceral and somatic pain is useful, it is important to realize that some pathological conditions will result in a mixed picture. For example, acute appendicitis classically presents with acute abdominal pain that is initially felt in the umbilical area resulting from appendicular obstruction, which gradually localizes to the right iliac fossa and becomes sharper in nature as the overlying parietal peritoneum becomes inflamed.

Inflammation

Acute inflammation of an intra-abdominal organ or the peritoneum may occur as a result of a variety of irritants. These may be broadly classified into infective or non-infective in nature (Table 12.4).

Table 12.4 Injurious agents causing inflammation

Peritonitis

Inflammation of the peritoneum (peritonitis) may be classified according to extent (either localized or generalized) and aetiology (Table 12.5). In a surgical setting, the most common cause of generalized peritonitis is perforation of an intra-abdominal viscus. Inflammation of the peritoneum results in an increase in its blood supply and local oedema formation. There is transudation of fluid into the peritoneal cavity, followed by the accumulation of a protein-rich fibrinous exudate. In the normal state, the greater omentum constantly alters its position within the abdominal cavity as a result of intestinal peristalsis and abdominal muscle contraction. In the presence of inflammation, the greater omentum will adhere to and surround the abnormal organ. The fibrinous exudate effectively glues the omentum to the inflamed viscus, walling it off and preventing the further spread of inflammation. In addition, the exudate inhibits intestinal peristalsis, resulting in a paralytic ileus which also limits the spread of the inflammation and infection. As a result of the ileus, fluid accumulates within the lumen of the intestine and, along with the formation of large volumes of intra-peritoneal transudate and exudate, this will lead to a decrease in the intravascular volume, producing the clinical features of hypovolaemia.

Table 12.5 Classification of peritonitis

Infarction

An infarct is an area of ischaemic necrosis caused either by an occlusion of the arterial supply or the venous drainage in a particular tissue, or by a generalized hypoperfusion in the context of shock (Table 12.6). The typical histological feature of infarction is ischaemic coagulative necrosis. An inflammatory response begins to develop along the margins of an infarct within a few hours, stimulated by the presence of the necrotic tissue.

Table 12.6 Aetiology of infarction

The consequences of decreased perfusion of a tissue depend on several factors: the availability of an alternative vascular supply, the rate of development of the hypoper- fusion, the vulnerability of the tissue to hypoxia, and the blood oxygen content. In the context of acute abdominal pain, intestinal infarction is the most common cause. Other organs that may infarct include the ovaries, kidneys, testes, liver, spleen and pancreas.

Perforation

Spontaneous perforation of an intra-abdominal viscus may be the result of a range of pathological processes. Weakening of the wall of the viscus, which might follow degeneration, inflammation, infection or ischaemia, will predispose to perforation. An increase in the intraluminal pressure of a viscus, such as occurs in a closed-loop obstruction (Fig. 12.2), will predispose to perforation, as will peptic ulceration, acute appendicitis and acute diverticulitis. Other less common causes are carcinoma of the colon, inflammatory bowel disease and acute cholecystitis.

Fig. 12.2 Volvulus: an example of closed-loop obstruction.

A Diagrammatic representation of a volvulus. B X-ray showing volvulus of sigmoid colon.

Perforation can also be iatrogenic, and may occur during the insertion of a Verres needle at laparoscopy, because of a careless cut or suture placement during surgery, and during the course of an endoscopic procedure.

History

The main presenting complaint of patients with an acute abdomen is pain. The characteristics of the pain (Table 12.7) give important clues to the likely underlying diagnosis, and these should be explored in depth. However, the importance of a full history cannot be overemphasized and is essential in all patients.

Table 12.7 Characteristics of abdominal pain

Site of pain

The site of abdominal pain is perhaps the most valuable pointer to the underlying diagnosis. In order to describe the site of pain, the abdomen is traditionally divided into either quarters or ninths (Figs 12.3 and 12.4).

Fig. 12.3 The four quadrants of the abdomen.

Fig. 12.4 The abdomen divided into ninths.

Onset of pain

The onset of pain can be sudden or gradual. Typically, pain from a perforation is sudden and that from inflammation is gradual. Patients with the former can usually remember exactly what they were doing at the time of onset, whereas in the latter localization in time is more difficult. The various characteristics of abdominal pain, as shown in Figure 12.5, are essential in helping the clinician formulate a differential diagnosis.

Fig. 12.5 Time vs intensity graphs for acute abdominal pain.

Examination

During the course of taking a history it is possible to form a general impression of the state of the patient. The unwell patient with acute abdominal pain may look pale and sweaty, lie flat on the bed, be cerebrally obtunded, and be unable to move without experiencing pain. Others, however, may look surprisingly well, have a good colour, sit up in bed, talk normally and be able to move freely. All these observations should be noted and recorded, along with the temperature, pulse, blood pressure and respiratory rate.

Other important features to look for on general examination include clinical evidence of anaemia, jaundice, cyanosis and dehydration. It is important to bear in mind that physical signs are often less obvious than might be expected in the elderly, the obese, the generally unwell and those taking steroids. As in every emergency patient, a full examination, including the cardiovascular, respiratory and neurological systems, in addition to the abdomen and pelvis, must be carried out and the results documented. Specific details relating to the abdominal examination are described below and in Table 12.8.

Table 12.8 Checklist for examination of the acute abdomen

In small children with abdominal pain, it is useful to ask the child to ‘blow out’ and ‘suck in’ their abdomen and to cough. These three movements will usually elicit pain in the presence of peritonism without laying a hand on the child’s abdomen. Rebound tenderness should never be elicited in children. Gentle tapping with the percussing finger will elicit the same information (tap tenderness) in a much less cruel way. The history of pain on moving or coughing is also a good indicative as to the presence of rebound tenderness.

Investigations

Following initial clinical assessment, and during assessment in the critically ill, measures should be taken to resuscitate the patient. During this period, further investigations can be organized to help in the diagnostic process. It is important to remember that in all patients a working list of differential diagnoses must be made after clinical assessment so that only appropriate investigations are instituted. There is no point in organizing investigations the results of which will not influence the clinical management.

The most common investigations carried out on the patient with acute abdominal pain include full blood count (FBC), urea and electrolytes (U&Es), amylase, C-reactive protein, liver function tests, plain radiology (erect chest and supine abdominal X-rays) and an ultrasound scan.

Dipstick testing

Haematuria may result from a wide range of conditions but in the context of acute abdominal pain may indicate a urinary tract tumour, infection or nephrolithiasis. Glucose or ketones in the urine indicate recent starvation or possible diabetic ketoacidosis. Protein, bilirubin or casts in the urine suggest renal or liver disease. In patients with an inflamed retrocaecal appendix, urine testing may demonstrate the presence of protein, and urgent microscopy (which will confirm or refute the presence of bacteria) should be arranged to determine whether there is an underlying urinary tract infection or whether another condition, such as appendicitis, might be the cause.

Bacteriology

If the clinical picture is suggestive of a urinary tract infection and the urine dipstick demonstrates blood, protein or nitrites, urgent microscopy and culture should be requested. Specimens from any other potential sites of infection should also be submitted for bacteriological analysis (stool, blood, pus etc.).

Pregnancy test

A pregnancy test should be performed in all women of childbearing age who present with acute abdominal pain and in whom the chance of pregnancy cannot be excluded. Not only is this important if X-rays are to be taken, but it will also reveal the possibility of an ectopic pregnancy if positive.

Urinary porphobilinogen

Quantitative assay of urinary porphobilinogen is the most important diagnostic test for porphyria, which is a rare condition that may present with acute abdominal pain and should be considered in difficult cases.

Plain X-rays

The role of plain radiography in the investigation of the patient with acute abdominal pain has been well studied. The erect chest X-ray (CXR) is the most appropriate investigation for the detection of free intra-peritoneal gas (Fig. 12.6) and should be carried out in any patient who might have a perforation. If the condition of the patient prevents an erect film being taken, then a left lateral abdominal decubitus film might be helpful. Although a visceral perforation is the most common cause of free intra-peritoneal gas, other causes exist and should be considered where appropriate (Table 12.10). An erect CXR is also useful in identifying a respiratory condition which may present with upper abdominal pain.

Fig. 12.6 Gas under the diaphragm seen on the erect chest X-ray in a patient with a perforated peptic ulcer.

Table 12.10 Causes of free subdiaphragmatic gas on abdominal X-ray

The role of plain abdominal radiographs remains controversial despite many studies that have demonstrated that, with the exception of suspected intestinal obstruction (Fig. 12.7), they rarely help in the diagnosis and have even less role in altering the clinical decision (EBM 12.1). However, the supine abdominal X-ray (AXR) can be of use in patients whose diagnosis is unclear and in whom the presence of calcification (e.g. ureteric colic) and abnormal gas shadows (e.g. possible intestinal ischaemia) may be helpful. They should however not be performed routinely, and have no role in the investigation of patients with suspected appendicitis.

Fig. 12.7 Abdominal X-rays in bowel obstruction.

A Supine film in a patient with small bowel obstruction showing valvulae comitantes.B X-ray demonstrating large bowel obstruction with arrow at a haustration.

An erect AXR is only of value in patients with intestinal obstruction, although it is well known that even then the information obtained over and above that from the supine film is small. In patients with suspected obstruction whose supine film does not show significant bowel dilatation, an erect film might reveal fluid levels.

Contrast radiology

Contrast may be administered orally, down a nasogastric or nasojejunal tube, or per rectum to examine the bowel in patients with acute abdominal pain. In the emergency setting, the contrast used is usually water-soluble, as free egress of barium into the peritoneal cavity can make subsequent surgery more difficult and will remain for a very long time making subsequent X-ray examinations more difficult to interpret. As water-soluble contrast does not adhere well to the bowel mucosa, the information obtained is less specific and detailed than with barium, but in the patient with acute abdominal pain, the main issue that requires the use of contrast X-rays is determining the presence or absence of obstruction or perforation.

In up to 50% of patients with a perforated peptic ulcer, no free gas can be identified on plain radiography. If the diagnosis remains uncertain based on clinical assessment, a water-soluble contrast meal might be diagnostic (Fig. 12.8). In patients with small bowel obstruction, a water-soluble small bowel follow-up can help not only in confirming or refuting obstruction, but also in predicting which patient is likely to require surgery. Failure of contrast to reach the caecum by 4 hours suggests obstruction and these patients will not usually settle with non-operative management (Fig. 12.9).

Fig. 12.8 Supine abdominal radiograph taken 20 min after oral administration of 50 ml of water-soluble contrast in a patient with suspected perforated peptic ulcer, in whom the erect chest radiograph was normal.

Note the small trickle of contrast through the perforation. These findings were confirmed at laparotomy

(from Ellis BW, Paterson-Brown S (eds) 2000 Hamilton Bailey’s Emergency Surgery, 13th edn. Hodder Arnold, with permission).

Fig. 12.9 Supine abdominal radiographs taken after oral administration of 50 ml of water-soluble contrast material.

A 90 minutes after administration. B 4 hours after. Note failure of contrast to reach the caecum and the obvious small bowel obstruction. Laparotomy confirmed small bowel obstruction due to adhesions. C90 minutes after administration of contrast in another patient showing contrast in the large bowel (arrows) excluding small bowel obstruction.

A water-soluble contrast enema used to be considered essential in the assessment of patients with large bowel obstruction in order to differentiate between pseudo-obstruction and an obstruction caused by a mechanical problem (Fig. 12.10). However computed tomography (CT) with rectal contrast is now more commonly performed (see Ch. 16). Carrying out an unnecessary operation on a patient with pseudo-obstruction is associated with a high morbidity and mortality and cannot be defended.

Fig. 12.10 Contrast radiology in the diagnosis of large bowel obstruction.

A and B Supine abdominal X-rays in patients with large bowel obstruction. C Contrast enema in patient A shows no mechanical cause, i.e. pseudo-obstruction. D An obstructing carcinoma of the sigmoid colon in patient B.

Intravenous pyelography confirms the diagnosis of renal obstruction by calculi and may be helpful in the diagnosis of other types of renal pain. Again CT is now more commonly used to detect renal tract calculi.

Ultrasonography

Ultrasound is the most common investigation used in patients with acute abdominal pain. As a general investigation it might reveal small amounts of intra-peritoneal fluid in conditions such as perforation and infection, whereas in specific conditions such as acute cholecystitis, biliary obstruction, aortic aneurysms and ovarian cysts it can be diagnostic. Although some studies have reported high levels of sensitivity and specificity in the diagnosis of acute appendicitis, ultrasonography in these cases is highly operator-dependent and a negative result cannot be relied upon, particularly if the clinical picture suggests otherwise.

Computed tomography (CT)

The current multi-slice CT scanners have such good organ definition that they are increasingly being used early in the investigation of the acute abdomen where they can reliably identify free intra-abdominal gas, ischaemic bowel, acute inflammation such as appendicitis and diverticulitis. In general, because of the radiation used, the use of CT should be limited to cases of diagnostic difficulty and to evaluate traumatic injuries and intra-abdominal sepsis in patients who may have an intra-abdominal collection or abscess, in addition to suspected leaking abdominal aortic aneurysms. Contrast-enhanced CT is also used routinely to detect pancreatic necrosis in patients with severe acute pancreatitis. CT should not be used routinely in young patients with suspected appendicitis.

Angiography

Mesenteric angiography used to be the investigation of choice in suspected mesenteric ischaemia, but has now been superseded by CT angiography, which can also reliably differentiate arterial from venous causes, and distinguish occlusive from non-occlusive disease. CT angiography can also be used in the diagnosis and management of lower gastrointestinal haemorrhage, although this rarely presents with acute abdominal pain. Obviously, if embolization is required, formal angiography is necessary.

Endoscopic investigations

Flexible sigmoidoscopy is commonly performed on patients who present with an acute abdomen associated with rectal bleeding and in those patients with large bowel obstruction to evaluate the anorectum. Additional information can be obtained from a colonoscopy. Furthermore, a sigmoid volvulus can often be deflated by careful sigmoidoscopy (see chapter 16). Upper gastrointestinal endoscopy is used to investigate patients with acute upper abdominal pain in whom a perforated peptic ulcer has been excluded, as discussed above.

Peritoneal lavage

Peritoneal lavage was used for many years as a first-line investigation in patients suspected of having intra-abdominal injury from trauma. However its use has now been taken over by CT. Many Emergency Departments are now using FAST (Focussed Abdominal Scans for Trauma); ultrasound scans in the immediate assessment of patients with abdominal trauma in order to identify free fluid (i.e. blood or bowel contents). In patients where free fluid is seen, CT scans can then be organized if required, or alternatively, depending on the state of the patients, immediate surgery can be planned. Occasionally some patients on the intensive care unit requiring large amounts of cardiac support are too unstable to be transferred to the CT scanner. In these patients peritoneal lavage can be helpful in confirming or excluding a surgical cause of a patient’s condition. It is carried out by inserting a dialysis catheter into the peritoneal cavity under local anaesthetic and infusing 1 litre of normal saline. The effluent is removed and examined for white cell count, amylase, bacteria and bile.

Laparoscopy

Many studies have demonstrated that laparoscopy (Fig. 12.11) can significantly improve surgical decision-making in patients with acute abdominal pain. It is particularly useful in patients for whom the decision to operate is in doubt, and in the elderly when findings from the history and examination can be misleading. Young women probably benefit the most from laparoscopy, as it is so difficult in this group to accurately differentiate acute appendicitis from acute gynaecological conditions, many of which do not require surgery. As laparoscopic appendicectomy increases in use, more patients will undergo diagnostic laparoscopy first.

Fig. 12.11 Diagnostic laparoscopy.

A Bleeding ovarian cyst. B Acute appendicitis.

Primary peritonitis

Primary peritonitis is uncommon, although in childhood it can account for up to 15% of acute abdominal emergencies. The condition used to be common in young girls following the ascent of pneumococcal or streptococcal infection from the genital tract.

Escherichia coli is now the predominant causal organism and probably gains access through the gut wall, or rarely by blood-borne spread from a distant focus. In adults, spontaneous bacterial peritonitis (SBP) may occur in patients with the nephrotic syndrome, but is more frequently seen in those with liver cirrhosis or chronic renal failure (particularly in patients on peritoneal dialysis). The mortality rate for patients with primary bacterial peritonitis varies from 20% to 80%.

Classically, diffuse peritonitis with generalized abdominal tenderness and rigidity develops within 24 hours. Fever and leucocytosis occur early. Abdominal rigidity is relatively uncommon. A sample of peritoneal fluid, which is usually turbid, is sent for Gram staining and bacterial culture. Antibiotic therapy is the mainstay of treatment, but either laparoscopy or laparotomy may be needed to rule out a surgical cause, if this is suggested by the culture of enteric organisms.

Postoperative peritonitis

Peritonitis after abdominal surgery may be a residual effect of the original disease or a direct complication of its operative management (e.g. anastomotic leakage). Diagnosis is difficult, as:

Persisting abdominal distension or the development of vomiting and distension after an initial return to normality should raise the suspicion of peritoneal infection. Suspicion is heightened if the patient looks unwell and has fever, tachycardia and an altered mental state. Plain abdominal films may merely show dilatation of the intestine and ultrasonography can be used to detect collections. However contrast enhanced CT with oral contrast/rectal contrast is the best investigation and will identify anastomotic leakage and any associated collections.

Fluid and electrolyte replacement, nasogastric suction and broad-spectrum antibiotic therapy are instituted, and the need for reoperation is considered. Patients with a small anastomotic leak which is well drained (by drains left at the time of the original surgery) may be managed non-operatively and intra-peritoneal collections can be drained by percutaneous drainage under radiological guidance. Patients with more widespread peritonitis require repeat laparotomy. There is an increasing role for re-look laparotomy in patients with severe sepsis identified at the time of the first operation in order to further washout the peritoneal cavity, if after the first few days they are still exhibiting signs of severe sepsis. This is usually preceded by CT to help identify any collections which may have occurred.

Intra-abdominal abscess

An intra-abdominal abscess may develop in conjunction with an underlying inflammatory process or be a complication of peritonitis or intra-abdominal surgery. The abscess gives rise to pyrexia, tachycardia and clinical signs of toxicity. Leucocytosis and raised C-reactive protein are usual. Common sites for abscess formation are the subphrenic and subhepatic spaces, the pelvis, and between loops of bowel. Complications include rupture with generalized peritonitis, the erosion of blood vessels with potentially catastrophic bleeding, and septicaemia. Occasionally, subphrenic abscesses rupture into the pleural cavity, and pelvic abscesses sometimes discharge spontaneously through the rectum.

The site of the abscess may be suspected from the history and clinical examination, but localizing signs can be surprisingly few, particularly with subphrenic abscess, hence the expression ‘pus somewhere, pus nowhere else, pus under the diaphragm’. Unexplained fever after peritoneal infection or operation should always raise the suspicion of abscess formation. Tachycardia is usual. Pain and tenderness over the ribcage, shoulder-tip pain and a ‘sympathetic’ pleural effusion strengthen the suspicion of subphrenic abscess, whereas urgency of defaecation, diarrhoea and a boggy swelling in the pouch of Douglas on rectal examination are features of a pelvic abscess (Fig. 12.12).

Fig. 12.12 Rectal examination for pelvic abscess.

Ultrasound and/or CT are of immense value in diagnosis (Fig. 12.13), aspiration to obtain material for bacteriological culture and subsequent drainage. However, surgical drainage may still be needed to ensure effective drainage, particularly if the collection is loculated. Pelvic abscesses frequently rupture spontaneously into the rectum, but may require incision and drainage through the anterior rectal wall. Antibiotic therapy is used in conjunction with drainage of the abscess. Signs usually resolve rapidly following effective drainage.

Fig. 12.13 CT scan of upper abdomen showing pancreatic abscess containing streaks of gas.

Complications

Gangrenous appendicitis and perforation tend to occur after a significantly more prolonged period of pain than uncomplicated appendicitis. Generalized peritonitis results if the inflamed area is not walled off by omentum and loops of bowel. If walling off does occur, either an appendix mass or an abscess will develop. A perforated pelvic appendix will lead to a pelvic abscess, and on examination there may be very little in the way of abdominal signs.

Investigations

The various investigations used in patients with suspected appendicitis have already been discussed earlier in the chapter. However, the diagnosis of acute appendicitis is based on clinical assessment and there are no specific diagnostic tests. Ultrasonography in skilled hands might demonstrate a swollen non-compressible appendix, free fluid or even a mass in the right iliac fossa. If, after clinical assessment, the diagnosis remains in doubt, the clinician must proceed along one of two lines: either to carry out laparoscopy and undertake appendicectomy if indicated, or to institute a short policy of close and repeated observation with reassessment every hour. On occasions when there is diagnostic difficulty, and particularly in the elderly, abdominal CT can be helpful in making the diagnosis in addition to excluding other conditions (Fig. 12.16).

Fig. 12.16 CT scan demonstrating perforated appendicitis.

The thickened and inflamed appendix can be seen extending from the caecum medially associated with some flecks of gas near the tip.

Management

The treatment of appendicitis is almost always surgical; increasingly, laparoscopic appendicectomy is being carried out, especially if a diagnostic laparoscopy has been performed first to establish the diagnosis (EBM 12.2). Although the laparoscopic approach is undoubtedly associated with less postoperative pain, most studies have so far failed to show significant advantages in shortening hospital stay or returning to normal activities. This is probably because of the underlying sepsis, which slows recovery. It is also possible to treat patients who do not have overt peritonitis non-operatively with antibiotics, and this is often done in areas of the world where ready access to surgery is impossible. In these conditions, there is a high incidence of recurrent problems and as such this practice is not favoured. If, by the time the patient presents, a mass can be felt, non-operative management with intravenous fluids and antibiotics is the treatment of choice, provided there are no signs of peritonitis (when an operation should be carried out). In these patients, an ultrasound scan should be arranged to look for an underlying abscess; if one is present, it should be drained either under radiological guidance or surgically.

Following successful non-operative treatment of an appendix mass, it used to be traditional practice to carry out an interval appendicectomy 3–6 months later. This prevents further attacks, and in the elderly makes sure that there is no underlying carcinoma of the caecum. However, several studies have now confirmed that after the successful non-operative treatment of either an appendix mass or an abscess, only a few patients develop recurrent problems, and most of them do so within the first few months. It is therefore reasonable not to carry out an interval appendicectomy unless the patient experiences further symptoms or complications (EBM 12.3). It is still important, especially in older patients, to exclude a carcinoma of the caecum by either double-contrast barium enema or colonoscopy. An interval appendicectomy should be undertaken if this course is not pursued.

Mittelschmerz and ruptured corpus luteum

The Graafian follicle normally ruptures 14 days after the start of the last menstrual period, and release of the ovum may be complicated by bleeding. The follicle normally becomes a corpus luteum, which degenerates before the start of the next period unless conception occurs. Bleeding from the corpus luteum is an occasional cause of pain in the late stages of the menstrual cycle.

Patients with these causes of pain are usually between 15 and 25 years of age, and experience sudden pain in one or other iliac fossa. Tenderness and guarding in the right iliac fossa can simulate acute appendicitis, and a few patients bleed sufficiently to suggest rupture of an ectopic pregnancy. Rectal or vaginal examination may reveal tenderness in the rectovaginal pouch. Ultrasonography may demonstrate free fluid in the pelvis.

The patient is treated non-operatively, unless appendicitis or ruptured ectopic pregnancy cannot be excluded when laparoscopy should be performed.

Ruptured ectopic pregnancy

A fertilized ovum implants at an abnormal site in 1 in 200 pregnancies; the fallopian tube is by far the most common site. The erosive trophoblast may penetrate the wall of the tube, and often ruptures after about 6 weeks. Alternatively, the conceptus may be extruded from the fimbrial end of the tube.

Bouts of cramping iliac fossa pain may be associated with fainting and vaginal bleeding. Rupture produces sudden severe pain, bleeding and circulatory collapse, with the abdominal pain often becoming generalized. Immediate surgery is required. A missed period is reported by most patients and a raised beta human chorionic gonadotrophin (β-HCG) level in the presence of abdominal pain should always raise the suspicion of an ectopic pregnancy.

Complications of an ovarian cyst

Benign ovarian cysts are a common cause of torsion, rupture and bleeding. Dermoid cysts often have a long pedicle and account for 50% of torsions in young women. Pain from rupture/bleeding can be sudden and severe and may mimic other causes of lower abdominal peritonitis, particularly acute appendicitis.

Pain from a torted ovarian cyst is often severe and cramp-like and sometimes associated with a smooth round mobile mass that lies higher in the abdomen than might be expected. Tenderness and guarding may be present. Torsion of a fibroid may produce a similar picture.

At laparoscopy the twisted pedicle is transfixed and ligated and the cyst is removed. Care must be taken to avoid rupture in case the cyst is malignant. Further radical surgery may be needed if histological examination reveals malignancy. In many cases the cyst has actually resulted in torsion of the whole ovary and by the time of surgery this is usually dead and requires removal, although if caught early untwisting may result in salvage of the ovary. Obviously in all such cases the gynaecology team should be involved in management.

Acute salpingitis

Acute salpingitis is most commonly caused by chlamydial infection, but streptococcal, gonococcal or even tuberculous infection can also be responsible. Both tubes are often involved and adhesions may seal the fimbriated end, producing a pyosalpinx, and subsequent infertility.

Bilateral pain is felt just above the pubis and inguinal ligaments. There may be urinary frequency, irregular menstruation, pyrexia, leucocytosis and raised C-reactive protein. Vaginal examination reveals unusual warmth, a tender cervix and a vaginal discharge. The cervix appears red and inflamed, and a swab reveals the causative organism. Vaginal findings may be less marked when there is a closed pyosalpinx.

Treatment consists of antibiotic therapy. Laparoscopy is used increasingly to avoid unnecessary laparotomy if acute appendicitis cannot be ruled out. The tubes appear inflamed and oedematous, and ‘milking’ them gently produces a purulent discharge from which a bacteriological swab can be taken.