Endgames Picture Quiz

The acute abdomen

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2549 (Published 24 April 2013) Cite this as: BMJ 2013;346:f2549
  1. B H van Duren, foundation year 1 doctor1,
  2. M Moghul, core surgical trainee year 11,
  3. S G Appleton, consultant2,
  4. G I van Boxel, core surgical trainee year 22
  1. 1Department of General Surgery, Horton General Hospital, Banbury OX16 9AL, UK
  2. 2Department of General Surgery, Wycombe General Hospital, High Wycombe HP11 2TT, UK
  1. Correspondence to: G I van Boxel gijs.vanboxel{at}gmail.com

A 45 year old woman presented to the emergency department with an eight hour history of sudden onset abdominal pain. The pain was severe, sharp, and worse on movement. She felt nauseous but had not vomited. She had last opened her bowels earlier that day, passing a small amount of hard stool. Her medical history included osteogenesis imperfecta, which caused hip pain, and for which she took 140 mg of oxycodone daily.

On examination she was in obvious distress. She was tachypnoeic at 22 breaths/min and tachycardic at 110 beats/min. Blood pressure, peripheral oxygen saturation, and temperature were all in the normal range. Her abdomen was exquisitely tender to palpation, with maximum tenderness in the right iliac fossa, localised guarding, and percussion tenderness. Digital rectal examination identified hard faeces in the rectum. Bowel sounds were absent. Initial blood tests showed haemoglobin 14.5 g/L (reference range 12.0-15.0), white cell count 17.5×109/L (4.0-11.0), C reactive protein 5.5 mg/L (0-8). Urea, electrolytes, and liver function tests were normal. A venous blood gas showed a raised lactate of 4.2 mmol/L (0.5-2.0; 1 mmol/L=9.01 mg/dL). Urgent chest radiography (in the erect position) was performed (fig 1).


  • 1 What abnormality is apparent on the erect chest radiograph?

  • 2 What is the sensitivity of this radiological sign?

  • 3 What is the differential diagnosis?

  • 4 What immediate management should be implemented for this patient?

  • 5 What definitive treatment options should be considered?


1 What abnormality is apparent on the erect chest radiograph?

Short answer

The erect chest radiograph shows a pneumoperitoneum with free gas under the diaphragm bilaterally.

Long answer

The erect chest radiograph shows crescentic collections of gas under the diaphragm bilaterally. The right hemidiaphragm is clearly delineated, with gas above and below (fig 2). In addition, the gas indicated by the broken arrows may be under the central tendon of the diaphragm, but may also lie anterior to the central tendon. This sign is called a “continuous diaphragm sign” or a “cupola sign.”


Fig 2 Erect chest radiograph showing gas above and below the right hemidiaphragm (solid arrows) as well as gas under, and perhaps anterior to, the central tendon of the diaphragm (broken arrows)

2 What is the sensitivity of this radiological sign?

Short answer

The diagnostic sensitivity of this sign depends on its cause, varying from 8% in perforated appendicitis to 94% in perforated peptic ulcer disease. The overall sensitivity of detecting gas under the diaphragm on erect chest radiography in the context of a perforated hollow viscus is 69%.

Long answer

Erect chest radiography is useful for investigating hollow viscus perforation in patients presenting with abdominal pain. Four studies have reported its sensitivity for detecting free gas in the presence of hollow viscus perforation.1 2 3 4 We excluded the many other studies in this area that combined multiple plain film techniques (for example, abdominal, supine, or lateral decubitus films) or looked at iatrogenic pneumoperitoneum from our analysis (table).5 6 7 8 The level of evidence put forward by these studies varied greatly, with cohort sizes ranging from seven to 94 and reported sensitivities of 40-85% (table). In total, the studies looked at 195 patients with confirmed pneumoperitoneum (by means of surgery); 135 (69%) had free gas under the diaphragm on erect chest radiography, giving an overall sensitivity for this test of 69%.

Published studies on the sensitivity of pneumoperitoneum for hollow viscus perforation

View this table:

We could not assign a value for the negative predictive value of this test because the incidence of negative tests in the absence of perforated hollow viscus was not reported. Therefore, it cannot be assumed that a negative test rules out perforated hollow viscus.

Several factors influenced detection of gas under the diaphragm: the site of the perforation, symptom duration, the amount of free gas, and the radiographic technique. One study reported that the sensitivity of gas under the diaphragm associated with visceral perforation (on erect abdominal or erect chest plain radiography) varied with the anatomical site and cause of the perforation.6 Only five of 65 cases of appendicular perforation were associated with gas under the diaphragm, as opposed to 94% (810/860) of gastric or duodenal perforations. Another study also found a higher incidence of free gas on imaging (plain abdominal radiography and computed tomography) in gastric and duodenal perforations (8/11) than in appendicular perforations (3/39).9

The sensitivity of erect chest radiography also depends on the amount of free gas. Studies suggest that chest radiographs can detect as little as 1 mL of free air.2 3 4 6 One study noted that sensitivity decreases with reducing size of free gas pockets.5 Sensitivity is also dependent on meticulous radiological technique—the patient must be kept in a left lateral decubitus position for 10-20 minutes, followed by 10 minutes in the erect position before erect chest radiography is performed.8 10 11 12 Interestingly, the sensitivity of this test for detecting pneumoperitoneum caused by penetrating trauma or iatrogenic causes is consistently lower than that reported for pathological hollow viscus perforation.5 13 This could be because there is a smaller amount of air, or, more likely, in the setting of trauma, the quality of erect chest radiography is substandard. Transcutaneous ultrasonography is an additional, or alternative, investigation (particularly in the setting of trauma), although it is more susceptible to operator dependent variance. This technique does not require the patient to stand and may have a higher sensitivity, specificity, accuracy, and negative predictive value than plain radiography in the detection of pneumoperitoneum.14

3 What is the differential diagnosis?

Short answer

Free gas on erect chest radiography in the context of acute onset abdominal pain indicates perforation of a hollow viscus until proved otherwise. The most common causes are perforated peptic ulcer (16%), perforated diverticular disease (16%), perforated carcinoma (sigmoid, rectal, or caecal; 14%), and perforation secondary to ischaemia (10%). Perforated appendix secondary to appendicitis is common, but is less likely to cause a substantial amount of gas under the diaphragm.

Long answer

Apart from the conditions above, other differential diagnoses include perforated inflammatory bowel diseases, as a complication of toxic megacolon in ulcerative colitis, or as a perforation with local abscess or fistula formation in Crohn’s disease. Furthermore, about 10% of pneumoperitoneums detected radiologically occur without visceral perforation.15 16 Free gas can enter the peritoneum in other ways—through the thorax7 17 or through the female genital tract (for example, during waterskiing) or as a result of perforation.18 19 Gas can also be introduced iatrogenically—for example, during an endoscopic procedure or after surgical exploration.9 Lastly, clinicians should always be aware of conditions that can mimic pneumoperitoneum on erect chest radiography. An exam favourite is Chilaiditi’s syndrome, caused by a loop of bowel (usually transverse colon) between the liver and the diaphragm, which has the appearance of gas under the right hemidiaphragm.20

4 What immediate management should be implemented for this patient?

Short answer

The patient should be resuscitated according to advanced life support principles of “airway, breathing, and circulation” (ABC), and sepsis should be treated according to the sepsis six care bundle. When stable, computed tomography may be performed to aid in diagnosis and guide further management; alternatively, the patient may require an emergency laparotomy without further imaging.

Long answer

The immediate management of this patient should be in line with the management of any acutely unwell patient: “airway, breathing, circulation” (Resuscitation Council UK adult advanced life support algorithm 2010). The patient was tachycardic, tachypnoeic, and had a raised white blood cell count on admission; all of these are criteria for the diagnosis of systemic inflammatory response syndrome (box). The combination of the systemic inflammatory response syndrome and the presence of known or suspected infection is sufficient for a diagnosis of sepsis. Hollow viscus perforation is a source of infection, so the patient should be treated according to the sepsis six care bundle.21 22

Systemic inflammatory response syndrome criteria

  • Temperature: <36°C or >38°C

  • Heart rate: >90 beats/min

  • Respiratory rate: >20 breaths/min or partial pressure of carbon dioxide 4.3 kPa

  • White blood cell count: <4×109/L or >12×109/L or 10% immature bands

  • The syndrome is defined by a score ≥2.

Blood should be sampled for culturing and antibiotics given without delay. Intravenous fluid should be administered and urine output measured, aiming for a urine output of more than 0.5 mL/kg/h. Haemoglobin and lactate should be measured and oxygen given. The patient should receive adequate analgesia. The patient should be kept “nil by mouth” and may benefit from a nasogastric tube to empty the stomach. This is particularly important in a peptic perforation to reduce further peritoneal contamination. Once the patient is stable, a cause should be identified. Plain radiography is useful—either erect chest radiography or abdominal radiography. Free gas on an abdominal radiography may give rise to Rigler’s sign—the appearance of gas on both sides of the bowel wall. Computed tomography is the radiological gold standard for the diagnosis of hollow viscus perforation and aids the surgeon in operative planning.

5 What definitive treatment options should be considered?

Short answer

Definitive treatment depends on the cause. Patients often need surgery—either a laparoscopic wash-out or laparotomy. In some instances, a confined perforation is self limiting and can be treated non-operatively with antibiotics, bowel rest, and regular surgical review.

Long answer

The most common causes of visceral perforation are peptic ulcer disease (16%), diverticular disease (16%), blunt or penetrating trauma (14%), cancer (14%), and ischaemia (10%). Appendicitis and endoscopy account for 6% and 4%, respectively.9 Because of the multiple causes, the definitive management varies. In the absence of generalised peritonism, non-operative management with antibiotics, intravenous fluid resuscitation, and gut rest may be appropriate, but surgery is usually needed. The site of perforation, any comorbidities, and the operating surgeon’s preferences all contribute to deciding the most appropriate procedure. The aim is to achieve source control. The management of the two most common causes of visceral perforation is discussed.

Peptic ulcer disease refers to ulceration of the stomach and the duodenum. The incidence of this disease has dramatically decreased since the discovery of the association with, and successful management of, Helicobacter pylori.23 Perforated peptic ulcer disease is almost always managed operatively, although available evidence does not entirely back up this trend. Studies have found equivalent outcomes for non-operative and operative management in patients under 70 years without peritonism.24 25 However, all studies stipulate that assessment must be performed by an experienced surgeon and non-operative management promptly abandoned if the patient deteriorates.24 25 26 The operative management of perforated peptic ulcer disease depends on the location and site of the perforation. Commonly the perforation is plugged with an omental patch, which retains its own blood supply. A randomised trial has shown no difference in mortality between performing this procedure laparoscopically or openly.27 If the patient is haemodynamically unstable a partial gastrectomy may be performed (often by means of a linear stapler). In the context of gastric ulcer disease, it is important to obtain a sample for histopathology because the underlying cause may be cancer. If the patient is stable it may be possible to obtain a frozen section for analysis to exclude cancer. If the perforation proves to be caused by a benign gastric ulcer, the surgeon may perform a distal gastrectomy with either a Billroth I or a Billroth II gastroduodenostomy. H pylori must be tested for and treated if present. Lastly, any non-steroidal anti-inflammatory drugs must be stopped.

Diverticular disease is characterised by outpouchings of colonic mucosa and submucosa through weaknesses in the muscle layers of the colonic wall. The condition typically affects the sigmoid colon and its prevalence increases with age.28 Perforation of the colon secondary to diverticulitis is seen in 5-10% of people admitted with diverticulitis.29 The Hinchey classification of perforated diverticulitis comprises four grades: localised abscess formation (grade I), a pelvic abscess (grade II), purulent peritonitis (grade III), and faecal peritonitis (grade IV).30 A recent review suggests that grades I-III may be initially managed with intravenous antibiotics, laparoscopic wash-out, and drainage.31 Until recently, these patients were often managed with laparotomy and stoma formation.32 Faecal peritonitis requires a laparotomy, with resection of the affected bowel and stoma formation. Ultimately, the decision on whether surgery is appropriate and what type of access and treatment are needed (laparoscopic v open, stoma v primary anastomosis, damage control surgery v definitive surgery) depends on associated comorbid diseases.

Patient outcome

Computed tomography showed a perforation of the sigmoid colon. The patient underwent laparotomy. A 2-3 cm ovoid perforation of the antimesenteric border of the sigmoid was found, with multiple golf ball sized impacted faeces within the colon and abdomen. The abdomen was washed out and a Hartmann’s procedure performed with formation of an end colostomy. She made a full recovery. Histopathology of the resected specimen showed the underlying disease to be stercoral perforation.


Cite this as: BMJ 2013;346:f2549


  • Competing interests: We have read and understood the BMJ Group policy on declaration of interests and declare the following interests: None.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent obtained.