Differential Diagnosis

The patient presents with severe gastrointestinal symptoms, renal impairment, and electrolyte imbalances. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Severe Gastroenteritis with Acute Kidney Injury (AKI): The high frequency of diarrhea, vomiting, and subsequent development of paralytic ileus, along with oliguric AKI (indicated by high urea, creatinine, and phosphate levels, and the presence of granular casts), points towards a severe gastrointestinal infection leading to dehydration and renal failure.
• Other Likely diagnoses
  • Intestinal Obstruction: The development of paralytic ileus could also suggest an intestinal obstruction, which could be due to various causes including adhesions, hernias, or tumors. The obstruction could lead to vomiting and diarrhea, and if not promptly relieved, could result in renal impairment due to dehydration and possible bowel ischemia.
  • Sepsis: Given the severity of symptoms, sepsis from a gastrointestinal source (e.g., perforation, severe infection) is a possibility. Sepsis can lead to AKI, and the presence of high phosphate and granular casts supports renal involvement.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Mesenteric Ischemia: Although less common, mesenteric ischemia could present with severe abdominal symptoms, including diarrhea and vomiting, followed by ileus. It's a surgical emergency and can lead to AKI due to systemic inflammation and ischemic damage to the kidneys.
  • Toxic Ingestion: Certain toxic ingestions (e.g., ethylene glycol, methanol) can cause severe metabolic derangements, including high anion gap metabolic acidosis, renal failure, and neurological symptoms. The presence of high phosphate and AKI could be consistent with such an ingestion.
• Rare diagnoses
  • Hemolytic Uremic Syndrome (HUS): Typically associated with E. coli infections, HUS could explain the renal failure and might be preceded by gastrointestinal symptoms. However, it's less likely given the prominent ileus and the pattern of electrolyte imbalance.
  • Pigment Nephropathy (Rhabdomyolysis): If there was significant muscle breakdown (possibly from severe dehydration, sepsis, or another cause), it could lead to AKI. However, the primary symptoms do not strongly suggest muscle injury as the initial presentation.