In a 55‑year‑old female who accidentally took an excess dose of long‑acting insulin and has a ureteral stent placed two months ago without follow‑up, which laboratory studies and diagnostic tests should be obtained?

Immediate Laboratory and Diagnostic Workup

In this patient with accidental long-acting insulin overdose, immediately obtain serial glucose monitoring (every 1-2 hours), serum insulin level, C-peptide, and β-hydroxybutyrate during any hypoglycemic episode, along with urgent imaging (ultrasound or non-contrast CT) to evaluate the neglected ureteral stent given the concerning findings of pyuria, bacteriuria, elevated creatinine (3.55-3.63), and leukocytosis. 1

Critical Insulin Overdose Management

The patient's glucose has stabilized (recent values 80-182 mg/dL) after what appears to be resolution of the acute insulin effect, but vigilance remains essential:

• Continue frequent glucose monitoring (every 1-2 hours initially, then every 4 hours for at least 24-48 hours) as long-acting insulin can cause prolonged hypoglycemia lasting up to 7 days, particularly with high-concentration formulations 2
• During any hypoglycemic episode (glucose <55 mg/dL), immediately measure:
  • Plasma insulin level (≥3.0 µU/mL indicates hyperinsulinism)
  • C-peptide (≥0.6 ng/mL suggests endogenous production; low levels confirm exogenous insulin)
  • β-hydroxybutyrate (≤2.7 mmol/L indicates insulin-mediated suppression)
  • Screen for oral hypoglycemic agents to exclude polypharmacy 1

Key pitfall: Insulin measurement has significant pre-analytic challenges including degradation and adsorption to tubes; use appropriate collection tubes and process immediately 3. The distinction between exogenous and endogenous insulin via C-peptide is critical here.

Urgent Urological Evaluation

The neglected 2-month-old ureteral stent combined with current laboratory findings demands immediate attention:

Concerning Features Present:

• Severe renal dysfunction: Creatinine 3.48-3.63 (eGFR 14-15) with metabolic acidosis (CO2 17-19, pH 7.27)
• Active infection: Leukocytosis (15.5-15.9), neutrophilia (10.49), turbid urine with many bacteria and >50 RBCs
• Anemia worsening: Hemoglobin dropped from 9.5 to 8.1, macrocytic (MCV 100-105)

Required Imaging:

Obtain non-contrast CT abdomen/pelvis immediately (already ordered per your data) to assess:

• Stent position and potential migration
• Hydronephrosis persistence
• Ureteral perforation or periureteral abscess (rare but life-threatening complication in diabetic patients with chronic obstruction) 4, 5
• Stone burden and stent encrustation

Rationale: Forgotten stents in diabetic patients carry extreme risk for emphysematous infections, periureteral abscess, and ureteral perforation due to fragile, infected ureteral walls 4, 5. The combination of diabetes, chronic infection, and 2-month stent retention creates a perfect storm for catastrophic complications.

Additional Urological Labs:

• Urine culture (already pending) - essential for targeted antibiotic therapy
• Blood cultures (already pending) - given fever history and leukocytosis, rule out urosepsis

Metabolic Acidosis Workup

The patient has non-anion gap metabolic acidosis (anion gap 12, CO2 17-19, pH 7.27):

• This pattern with severe renal dysfunction (eGFR 14) suggests type 4 renal tubular acidosis from chronic kidney disease
• The hyperkalemia trend (4.6→5.1) and hyperphosphatemia (6.0) support advanced CKD
• No additional specific testing needed for the acidosis itself; it's explained by the renal failure

Anemia Investigation

Progressive macrocytic anemia (Hgb 9.5→8.1, MCV 100-105) requires:

• Vitamin B12 and folate levels - macrocytosis suggests nutritional deficiency
• Reticulocyte count - assess bone marrow response
• Iron studies if not recently done
• Consider erythropoietin level given advanced CKD (though treatment decision is clinical)

The anemia likely reflects combined CKD (erythropoietin deficiency) and nutritional deficiency (macrocytosis).

Monitoring Protocol

First 24-48 Hours:

• Glucose checks every 1-2 hours
• Continuous IV access for dextrose rescue
• Serial potassium monitoring (risk of hypokalemia during dextrose infusion or hyperkalemia from renal failure)
• Lactate if any signs of sepsis (current lactate 1.4 is reassuring)

Stent Management Timeline:

• Urgent urology consultation for stent removal/exchange within 24-48 hours once infection controlled
• Post-procedure imaging (ultrasound) at 2 weeks to assess hydronephrosis resolution 6
• If ureteral perforation or abscess found, may require percutaneous nephrostomy instead of stent manipulation 4

Critical caveat: Do NOT attempt stent manipulation if CT shows periureteral fluid collection or abscess - this requires drainage first and possible nephrostomy tube placement 4.