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Omental infarction is a rare cause of acute abdomen in childhood. We describe a case of omental infarction mimicking acute appendicitis occurring in a child with cyclical neutropenia. Neutropenic enterocolitis, a serious cause of the acute abdomen, has been linked with cyclical neutropenia. In neutropenic patients, omental infarction when diagnosed pre-operatively can be managed conservatively with the focus on improving the neutrophil count. If after imaging the diagnosis is in doubt, there should be a low threshold for laparoscopy. The low incidence of omental infarction will continue to mean that it is a diagnosis made at operation for suspected appendicitis. In these cases, the infarcted tissue may be removed by the laparoscopic or open technique.
A 16-year-old boy presented with a 24-h history of constant right iliac fossa pain. On examination, he was 154.6 cm tall (0.4th centile) and weighed 73.4 kg (91st centile), and his body mass index (BMI) was 30.6 kg/m2 (99th centile). Temperature was normal. On abdominal examination, tenderness and guarding were evident in the right iliac fossa. Clinical diagnosis was acute appendicitis.
This patient had history of cyclical neutropenia, a rare haematological condition in which neutropenia develops every 3–4 weeks. The neutropenia is often accompanied by pharyngitis, acute otitis media and apthous stomatitis. The condition was diagnosed at the age of 11 years by twice weekly serial differential blood counts over a 2-month period. A bone marrow biopsy was normal and anti-karyotype and anti-lymphocyte antibodies were negative. Treatment is with granulocyte-colony stimulating factor (G-CSF; 262 μg) four times a week which, although not eliminating the cyclical neutropenia, reduces its extent and hence the accompanying infections.
On admission, the neutrophil count was 1.82 × 109 cells/l. Pre-operatively, the patient was given a dose of G-CSF after discussion with the haematologist. At open operation, a normal retrocaecal appendix was removed and a 5-cm focal patch of necrosed omentum was excised (Fig. 1). Histopathology confirmed a normal appendix and omentum with focal fat necrosis. Postoperative recovery was uneventful and he was discharged 2 days later after liaison with the haematologist.
Omental infarction is a rare cause of acute abdomen in children.1 It is rarely diagnosed pre-operatively due to its low incidence and convincing mimicry of acute appendicitis. Indeed, most cases reported in the literature, as in our case, are diagnosed at operation for suspected appendicitis. Cyclical neutropenia is a rare haematological disorder characterised by periodic oscillations in the peripheral neutrophil count.2 Patients have a tendency to minor infections and ulcerative stomatitis, and rarely have overwhelming sepsis.3 Neutropenic enterocolitis, a serious cause of acute abdomen, has been linked with cyclical neutropenia4–6 and is associated with a high mortality.6 However, an extensive literature search did not reveal any reported cases of omental infarction in a child with cyclical neutropenia.
Omental infarction and omental torsion, two similar conditions, are classified as separate entities.7 Omental infarction is divided into primary and secondary. The infarction is termed primary when no cause can be found, while secondary infarction is associated with hyper-coagulable states, vasculitis and pancreatitis.8 Omental infarction occurs more commonly on the right half of the omentum. The distal right epiploic artery has been implicated in torsion and infarction occurring around the right gastrocolic ligament of the greater omentum. This tendency of the right side to infarct has been linked with anatomical variations of the omental pedicle, including bifid right omentum and increased mobility of that side.8
Despite being a rare condition, several risk factors have been identified. Obesity, as observed in our patient, is a recognised risk factor.8 It has been postulated that the increased fat deposition in the omentum of obese children outstrips the blood supply. Omental infarction may be differentiated from appendicitis, and importantly in the neutropenic patient, neutropenic enterocolitis, by the absence of gastrointestinal symptoms (including bloody diarrhoea in the case of neutropenic enterocolitis), fever, anorexia and a normal leukocyte count.4,8 If suspicion over a diagnosis remains, computed tomography has been shown to have a high sensitivity and specificity for diagnosis of omental infarction.9,10 Ultrasound provides a typical appearance of omental infarction of a hyperechoic, non-compressible mass adherent to the abdominal wall with overlying probe tenderness, although it is operator-dependent and has low sensitivity.11
When diagnosed pre-operatively by ultrasonography or computed tomography, omental infarction should be managed conservatively.10,12 However, the diagnosis of omental infarction is rarely made pre-operatively. Operative management in this case, open or laparoscopic, leads to rapid resolution of symptoms.1,8 The standard McBurney’s incision may be insufficient for diagnosis and resection as the infarcted tissue is often found in the right upper quadrant of the omentum; hence, laparoscopic surgery is recommended.1,8
It is common for paediatric surgeons to operate for suspected appendicitis on the basis of clinical examination rather than rely on pre-operative blood tests, and the neutrophil count may not be known at the time of operation. When a normal appendix is found at operation, the surgeon should actively seek out a cause for abdominal pain. This should include examining the right colon for signs of enterocolitis. In our case, the diagnosis of neutropenic omental infarction was made at the time of operation, so a trial of conservative management was not possible. When diagnosed pre-operatively, neutropenic omental infarction should be managed conservatively, with a focus in improving the neutrophil count with G-CSF, and supportive treatment with intravenous fluids and antibiotics. The management of neutropenic enterocolitis has been well described elsewhere.13–17 Conservative management is again advocated in the first instance, with a focus on improving the neutrophil count, after which neutropenic enterocolitis frequently ameliorates. Surgical management is indicated in peritonitis, pneumoperitoneum, shock, bowel wall necrosis, haemorrhage, abscess formation and deterioration after conservative management.17,18 In neutropenic patients where imaging has been equivocal, laparoscopy has been recommended.12
This case highlights the rare condition of omental infarction and, to the authors’ knowledge, the only case occurring in a child with cyclical neutropenia. Judicious use of imaging makes a pre-operative diagnosis of omental infarction possible, allowing conservative management in the first instance. Neutropenic enterocolitis has also been linked with cyclical neutropenia. The literature currently advocates conservative management for neutropenic patients with an acute abdomen. However, there are specific indications for surgical intervention including perforation, abscess formation, peritonitis and failed medical management. When the diagnosis after imaging in the neutropenic patient is in doubt, laparoscopy should be considered. In the absence of pre-operative blood tests and a normal appendix at operation, the surgeon should always seek to exclude neutropenic enterocolitis. The low incidence of omental infarction will continue to mean that it is a diagnosis made at operation for suspected appendicitis. In these cases, the infarcted tissue may be removed by the laparoscopic or open technique.