[A child with abdominal pain and fever: consider acute lobar nephritis - diagnostic considerations when the appendix is invisible on ultrasound].

Acute lobar nephritis (ALN) is a focal interstitial bacterial infection of the renal parenchyma. ALN is described as a midpoint between an acute pyelonephritis and renal abscess. ALN is underdiagnosed in children due to both non-specific symptoms and negative urinalysis/bacteriuria laboratory findings. The gold standard for diagnosis of ALN is CT scanning, however MRI can be considered to avoid radiation exposure. Diagnosing ALN is relevant, because it requires prolonged antibiotic treatment. Insufficient antibiotic treatment could cause renal scarring and subsequent hypertension or renal failure. Outpatient follow-up is indicated to exclude congenital urogenital abnormalities. We describe two paediatric patients with acute abdominal pain and fever who were suspected to have appendicitis (appendix not visualised by ultrasonography), but eventually were diagnosed with ALN and a renal abscess (despite absence of pyuria). These reports serve to highlight the issues around the recognition and diagnosis of ALN in children, and the need for clinicians to be mindful of this condition.