In a 70‑year‑old skilled‑nursing‑facility resident with diabetes mellitus, a kidney transplant on tacrolimus, a Foley catheter, and recent urinary retention who presents with acute confusion and a normal complete blood count, what are the likely reversible causes and what should the primary‑care physician do next?

Acute Confusion in a Skilled Nursing Facility Resident with Diabetes, Kidney Transplant, and Foley Catheter

The most likely cause of acute confusion in this patient is catheter-associated urinary tract infection (CAUTI), and the next step is to obtain urinalysis with culture, comprehensive metabolic panel, tacrolimus trough level, and fingerstick glucose immediately. 1, 2, 3

Most Likely Reversible Causes in This Patient

Infection (Highest Priority)

• Urinary tract infection is the most common precipitating factor for delirium in elderly patients, particularly in those with indwelling Foley catheters 1, 2
• The recent urinary retention episode followed by catheter placement creates high risk for CAUTI 1, 2
• Obtain urinalysis with microscopy and urine culture immediately, even though CBC is normal—systemic leukocytosis may be absent in immunosuppressed patients 3
• Blood cultures should be drawn if fever or systemic signs of infection develop 3
• Consider pneumonia as a secondary possibility and obtain chest X-ray if respiratory symptoms are present 1, 2

Tacrolimus Neurotoxicity (Critical in This Patient)

• Tacrolimus causes a spectrum of neurotoxicities including delirium, altered mental status, tremor, and posterior reversible encephalopathy syndrome (PRES) 4
• Neurotoxicity symptoms are associated with tacrolimus whole blood trough concentrations at or above the recommended range 4
• Check tacrolimus trough level immediately—if elevated, consider dose reduction or temporary interruption 4
• Diabetes mellitus increases tacrolimus concentrations, raising the risk of neurotoxicity in this diabetic patient 5

Metabolic Derangements

• Hypoglycemia is a critical reversible cause in diabetic patients and requires immediate point-of-care glucose testing 2, 3
• Obtain comprehensive metabolic panel to identify hyponatremia, hyperkalemia (tacrolimus causes this), renal dysfunction, or hepatic dysfunction 3, 4
• Tacrolimus-induced hyperkalemia can contribute to confusion 4
• Check thyroid-stimulating hormone and vitamin B12 level, as these represent reversible causes accounting for 1.7–2.6% of cognitive impairment 3

Medication-Induced Confusion

• Perform immediate medication reconciliation focusing on anticholinergics, benzodiazepines, opioids, and other high-risk medications 1, 2, 6
• Polypharmacy exponentially increases risk of drug-induced confusion in elderly patients 2
• Review all medications for drug-drug interactions with tacrolimus, particularly CYP3A inhibitors that increase tacrolimus levels and neurotoxicity risk 4

Immediate Diagnostic Workup (Next Steps)

Essential Laboratory Tests

• Fingerstick glucose immediately to rule out hypoglycemia 2, 3
• Urinalysis with microscopy and urine culture to identify UTI 3
• Comprehensive metabolic panel to assess electrolytes (especially sodium and potassium), renal function (creatinine, eGFR), and glucose 3, 4
• Tacrolimus whole blood trough level to assess for toxicity 4
• Complete blood count with differential—although already done and normal, review for subtle changes 3
• Thyroid-stimulating hormone and vitamin B12 as part of reversible dementia workup 3

Cognitive Assessment

• Use Brief Confusion Assessment Method (bCAM) or Confusion Assessment Method (CAM) rather than clinical impression alone to confirm delirium 1, 2, 3
• Key features distinguishing delirium from dementia: acute onset (hours to days), fluctuating course, disordered attention and consciousness 1, 2
• Delirium is frequently missed without structured screening tools 1, 2

Additional Testing Based on Clinical Context

• Blood cultures if fever, hypotension, or systemic infection suspected 3
• Chest X-ray if respiratory symptoms present 1
• Hemoglobin A1C to assess chronic glycemic control 3
• Consider neuroimaging (CT or MRI brain) only if focal neurological deficits, recent fall/trauma, or failure to improve with treatment of reversible causes 1, 3

Management Algorithm

Step 1: Stabilize and Assess

• Check fingerstick glucose immediately—treat hypoglycemia if present 2, 3
• Assess vital signs including orthostatic blood pressure 3
• Ensure adequate oxygenation and hydration 1

Step 2: Identify and Treat Infection

• Start empiric antibiotics for UTI if urinalysis shows pyuria, nitrites, or bacteria while awaiting culture results 1, 2
• In immunosuppressed transplant patients, do not delay antibiotic therapy 4
• Adjust antibiotics based on culture and sensitivity results 1

Step 3: Address Tacrolimus Toxicity

• If tacrolimus trough level is elevated or patient has tremor, altered mental status, or seizure, reduce dose or temporarily hold tacrolimus 4
• Monitor renal function closely, as tacrolimus causes nephrotoxicity that can worsen confusion 4
• Coordinate with transplant nephrology before making immunosuppression changes 4

Step 4: Optimize Medications

• Discontinue or minimize anticholinergics, benzodiazepines, and other high-risk medications 1, 2, 6
• Avoid physical and chemical restraints unless absolutely necessary for safety 1
• If sedation is required, haloperidol is preferred over benzodiazepines for acute agitated delirium 1

Step 5: Supportive Care

• Remove Foley catheter as soon as medically appropriate to reduce infection risk 1
• Provide frequent reorientation, visible clocks and calendars, adequate lighting, and familiar objects 1
• Encourage family presence at bedside 1
• Ensure adequate pain control, nutrition, and supervised mobility 1
• Use sensory aids (glasses, hearing aids) as appropriate 1

Critical Pitfalls to Avoid

• Never assume normal CBC rules out infection in immunosuppressed transplant patients—tacrolimus suppresses immune response and may mask typical inflammatory markers 4
• Never delay checking tacrolimus level in a confused transplant patient—neurotoxicity is a well-documented adverse effect that requires dose adjustment 4
• Never ignore hypoglycemia as a cause—diabetic patients on immunosuppression have unpredictable glucose metabolism 2, 3
• Never leave a Foley catheter in place longer than necessary—it is the leading cause of healthcare-associated UTI and delirium 1, 2
• Never use benzodiazepines as first-line sedation in elderly delirious patients—they worsen confusion and increase fall risk 1
• Never attribute confusion solely to "dementia" without systematic evaluation for reversible causes—delirium is superimposed on dementia in many cases 1, 2
• Never start antipsychotics without first addressing reversible medical causes—they carry black-box warnings for increased mortality in elderly patients with dementia 2

Special Considerations for Transplant Patients

• Tacrolimus increases risk of new-onset diabetes and hyperglycemia, which can contribute to confusion 4, 7
• Monitor for opportunistic infections including BK virus, CMV, and fungal infections in immunosuppressed patients 4
• Coordinate care with transplant team before making changes to immunosuppression regimen 4
• Tacrolimus-induced hypertension and hyperkalemia may contribute to altered mental status 4