Constipation and hemolytic uremic syndrome.

Standard diagnostic approaches for hemolytic uremic syndrome (HUS) rely on identifying a diarrheal prodrome. Prior research has shown that Shiga toxin-producing Escherichia coli (STEC) typically causes HUS with diarrhea preceding renal complications. However, this gap motivated exploration of cases where traditional diagnostic markers are absent. No prior work had resolved how to differentiate between STEC-HUS and atypical HUS (aHUS) in patients without diarrhea. Recognition of this diagnostic challenge remains limited in clinical settings. Delayed specimen collection can hinder STEC detection. Complement testing is commonly used for aHUS but may not clarify STEC-HUS cases. This uncertainty drove the need to examine clinical scenarios where diagnostic ambiguity persists despite available testing.

This case aimed to clarify diagnostic approaches when a patient presents with HUS but lacks a diarrheal prodrome. The specific problem involved a patient with abdominal pain and constipation, but no fecal specimen was available for initial testing. The motivation centered on understanding how to distinguish STEC-HUS from aHUS in such scenarios. Traditional diagnostic markers were absent, complicating clinical decision-making. The goal was to evaluate the impact of delayed specimen collection on diagnostic accuracy. Complement-blockade therapy was initiated based on suspicion of aHUS. Later confirmation of STEC-HUS highlighted the need for revised diagnostic strategies. This case sought to inform clinical management of similar patients.

The patient's clinical presentation was reviewed for signs of HUS. Pallor and abdominal pain were noted as key findings. Fecal specimen collection was delayed due to lack of diarrhea. PCR testing for Shiga toxin was performed once a specimen became available. Complement-pathway testing was conducted to rule out aHUS. Genetic variants and anti-Factor H antibodies were assessed. The absence of a diarrheal prodrome led to initial suspicion of aHUS. Complement-blockade therapy was administered before definitive testing results were available.

The patient was diagnosed with HUS based on clinical findings. No diarrhea was observed during the disease course. Fecal specimen collection was delayed for several days. PCR testing later confirmed Shiga toxin positivity. Complement-pathway testing failed to identify genetic variants or anti-Factor H antibodies. Complement-blockade therapy was discontinued after STEC-HUS was confirmed. The absence of a diarrheal prodrome initially suggested aHUS. This case highlights the diagnostic challenges of non-diarrheal STEC-HUS.

The authors propose that STEC-HUS can present without a diarrheal prodrome. This case supports the need for broader recognition of non-diarrheal STEC-HUS. Complement testing alone may not distinguish between STEC-HUS and aHUS. The diagnosis of aHUS remains a process of exclusion. Delayed specimen collection can hinder STEC detection. Clinical suspicion must be balanced with diagnostic limitations. STEC-HUS without diarrhea is rare but requires consideration. Future research is needed to better characterize these cases.