What is the diagnosis and management for a 42-year-old male with Down syndrome, presenting with epigastric pain, hypotension, bilateral pitting edema, elevated creatinine, normal Blood Urea Nitrogen (BUN), hemoglobin (Hgb) of 15.5, and White Blood Cell (WBC) count of 11.5?

Diagnosis: Acute Kidney Injury with Severe Renal Dysfunction

This 42-year-old male with Down syndrome presenting with epigastric pain, hypotension (BP 90/60), bilateral pitting edema, and markedly elevated creatinine (438.62 µmol/L or ~4.96 mg/dL) has acute kidney injury (AKI) with severe renal dysfunction requiring urgent fluid resuscitation, hemodynamic stabilization, and investigation for the underlying cause.

Immediate Clinical Assessment and Stabilization

Hemodynamic Management

• The hypotension (BP 90/60) with bilateral edema suggests a complex volume status requiring immediate assessment 1
• Establish IV access and initiate fluid resuscitation with normal saline bolus of 300-500 mL, followed by maintenance infusion of 40-80 mL/hour while monitoring for fluid overload 2
• Monitor for signs of pulmonary edema given the bilateral pitting edema already present 1
• Place urinary catheter for hourly urine output monitoring; oliguria (<400 mL/24h) indicates severe AKI 1

Critical Laboratory Workup

• The normal BUN with markedly elevated creatinine (438.62 µmol/L) is an unusual pattern that warrants specific investigation 3, 4
• Obtain complete metabolic panel including electrolytes (particularly potassium, which can be life-threatening in AKI), calcium, magnesium, and phosphate 4, 2
• Check arterial blood gas to assess for metabolic acidosis 1
• Obtain urinalysis with microscopy to evaluate for proteinuria, hematuria, and casts 4
• Measure urine sodium and osmolality to differentiate pre-renal from intrinsic renal causes 1

Down Syndrome-Specific Considerations

Increased Risk of Renal Abnormalities

• Individuals with Down syndrome have a 4.5-fold increased odds ratio for congenital kidney and urological malformations compared to the general population 5
• Down syndrome patients commonly have kidney hypodysplasia, obstructive malformations, and reduced kidney size 6
• Serum creatinine in Down syndrome patients is typically higher than in the general population even at baseline 5

Associated Comorbidities

• 44% of Down syndrome patients have congenital heart disease, which can contribute to cardiorenal syndrome 5, 7
• Evaluate for cardiac dysfunction with ECG and echocardiography, as heart failure can cause both hypotension and edema with renal hypoperfusion 1, 3

Differential Diagnosis for the Epigastric Pain

Rule Out Surgical Emergencies

• The combination of epigastric pain with hypotension and elevated WBC (11.5) requires exclusion of intra-abdominal catastrophe 1
• Obtain CT abdomen/pelvis with IV contrast (if renal function permits) or ultrasound to evaluate for:
  • Obstructive uropathy (more common in Down syndrome) 6
  • Bowel obstruction or perforation 1
  • Acute cholecystitis 1

Consider Renal-Specific Causes

• The markedly elevated creatinine with normal BUN suggests possible acute tubular necrosis or intrinsic renal disease rather than simple pre-renal azotemia 3, 4
• Renal ultrasound is essential to evaluate for:
  • Obstructive uropathy (hydronephrosis)
  • Kidney size and echogenicity
  • Structural abnormalities common in Down syndrome 4, 5

Management Algorithm

Immediate Actions (First 6 Hours)

1. Fluid resuscitation with careful monitoring - Start with 300-500 mL NS bolus, then 40-80 mL/hour maintenance 2
2. Discontinue all nephrotoxic medications - Stop NSAIDs, ACE inhibitors/ARBs in setting of hypotension 3, 4
3. Monitor hourly urine output - Target >0.5 mL/kg/hour 1
4. Correct electrolyte abnormalities - Particularly hyperkalemia which is life-threatening in AKI 2

Diagnostic Workup (First 24 Hours)

1. Renal ultrasound - To exclude obstruction and assess kidney structure 4
2. Echocardiography - To evaluate cardiac function given hypotension and edema 1
3. Abdominal imaging - CT or ultrasound to evaluate epigastric pain etiology 1

Nephrology Consultation

• Immediate nephrology consultation is indicated given:
  • Creatinine >4 mg/dL (438.62 µmol/L) 4
  • Unclear etiology of AKI 4
  • Potential need for renal replacement therapy if oliguria persists 1

Critical Pitfalls to Avoid

Volume Status Assessment

• Do not assume simple dehydration based on hypotension alone - The bilateral pitting edema suggests possible fluid overload despite hypotension, indicating cardiorenal syndrome 1, 3
• Avoid aggressive fluid resuscitation without monitoring for pulmonary edema 1

Medication Management

• Stop all NSAIDs immediately - They cause diuretic resistance and renal impairment through decreased renal perfusion 3
• Hold ACE inhibitors/ARBs in the setting of hypotension and AKI 3
• Adjust all medication doses for severe renal dysfunction (eGFR <30 mL/min) 4

Down Syndrome-Specific Considerations

• Do not overlook congenital urological abnormalities that may be contributing to AKI 5, 6
• Consider that baseline creatinine may be higher than general population norms 5

Monitoring Parameters

Short-Term (Every 4-6 Hours)

• Vital signs including orthostatic measurements 2
• Urine output 1
• Fluid balance 1
• Serum potassium 2

Daily Monitoring

• Serial BUN and creatinine to assess trajectory 4, 2
• Daily weights 2
• Complete metabolic panel 4

Prognosis and Follow-Up

• If AKI is due to pre-renal causes with prompt treatment, complete recovery is possible within 2 weeks 8
• However, individuals with Down syndrome have increased risk of chronic kidney disease and kidney failure, warranting long-term nephrology follow-up 5
• Quality of life and mental health are significantly impacted by kidney and urological impairments in Down syndrome patients 5