Differential Diagnosis for Acute Kidney Injury

Single Most Likely Diagnosis

• Diabetic Nephropathy: Given the patient's history of DMII on insulin and the presence of 4+ glucose in the urine, diabetic nephropathy is a likely cause of his acute kidney injury. The gradual increase in creatinine over six months also supports this diagnosis, as diabetic nephropathy can progress over time.

Other Likely Diagnoses

• Hypertensive Nephrosclerosis: The patient's history of hypertension (HTN) makes hypertensive nephrosclerosis a possible cause of his acute kidney injury. Chronic hypertension can lead to vascular changes in the kidneys, resulting in decreased renal function.
• Medication-Induced Nephrotoxicity: Although not specified, the patient may be taking medications (e.g., NSAIDs, certain antihypertensives) that can cause nephrotoxicity, leading to acute kidney injury.
• Chronic Kidney Disease (CKD) Progression: The patient's elevated creatinine and protein in the urine suggest CKD, which can progress over time, especially in the presence of comorbidities like DMII and HTN.

Do Not Miss Diagnoses

• Urinary Tract Obstruction: Although less likely, urinary tract obstruction (e.g., due to kidney stones, tumors) can cause acute kidney injury and must be ruled out, as it can lead to severe consequences if missed.
• Rapidly Progressive Glomerulonephritis (RPGN): RPGN is a rare but potentially life-threatening condition that can cause acute kidney injury. The presence of RBCs in the urine increases the suspicion for RPGN.
• Atheroembolic Disease: In patients with a history of HTN and atherosclerosis, atheroembolic disease can cause acute kidney injury. This diagnosis is critical to consider, as it can have a high mortality rate if not recognized and treated promptly.

Rare Diagnoses

• Vasculitis: Conditions like ANCA-associated vasculitis or polyarteritis nodosa can cause acute kidney injury, although they are less common in the elderly population.
• Amyloidosis: Amyloidosis can cause kidney damage and acute kidney injury, but it is a rare condition and would require further evaluation (e.g., kidney biopsy) for diagnosis.
• Sickle Cell Nephropathy: Although unlikely in an 80-year-old patient, sickle cell nephropathy can cause acute kidney injury in patients with sickle cell disease.