Case A 4 year old girl referred by the GP with acute abdominal pain, anorexia, fever and tachycardia. She exhibited generalised abdominal tenderness and distension with guarding in the RIF. She was grunting intermittently with fever. Initial investigation showed negative urine dip and a CRP of 7 with neutrophils of 10.6.

Following a differential diagnosis of appendicitis, and abdo/pelvic USS showed a large amount of free fluid with echogenic contents. The appendix was clearly visualised and was normal. Chest x-ray showed no free air under the diaphragm. The patient was treated with analgesia and was transferred out to a tertiary surgical unit as an acute surgical case to exclude intussusception, obstruction with possible. The repeat bloods showed CRP of 250 and was started on IV antibiotics.

Re-examination of the case revealed a two month history of intermittent bloating and eye puffiness which was being treated in the primary care as suspected dairy allergy. The patient was noted to have periorbital swelling and puffy hands.

Spontaneous bacterial peritonitis secondary to nephrotic syndrome was suspected. Repeat urinalysis showed 2+ of protein and 3+ of blood. Investigation revealed a urine albumin of 514 and ACR of 73.4 Blood cultures grew streptococcus and ASOT titers were 200untis/ml.

The patient was transferred back to DGH and was started on 60 mg/m² of daily oral prednisolone and penicillin prophylaxis. Since then she has had regular reviews in outpatient clinics and discussions with tertiary renal units. 3 months post presentation hasn't achieved remission yet and alternatives methods of treatment are being discussed.

Conclusion Differential diagnosis of acute abdominal pain in paediatrics is broad and challenging but peritonitis secondary to rupture appendix is the most common one. The child might be brought to hospital due to symptoms related to infection such as fever, abdominal pain, diarrhoea, lethargy. If the child’s proteinuria and oedema is not appreciated then the acute abdomen can be mistaken for peritonitis secondary to appendicitis. Untreated peritonitis can lead to septicaemia, meningitis and death. Children with nephrotic syndrome are at high risk of peritonitis during the period of heave proteinuria.