Why does the patient have renal failure?
How much of the patient's renal failure is chronic and how much is acute is difficult to determine at the time of admission. The elevated BUN/creatinine ratio and a low-normal blood pressure in a patient with hypertension and fever suggest that an element of dehydration might be present. The history of type 2 diabetes, retinopathy, and proteinuria make diabetic nephropathy with chronic renal failure a likely diagnosis, especially with the history of nephrologic evaluation.
In approximately 10% of diabetics with nephrotic-range proteinuria, renal biopsy will show that another disease is the cause of their proteinuria. These include primary kidney diseases, such as membranous glomerulopathy and focal segmental glomerulosclerosis, and systemic diseases, such as multiple myeloma or lupus nephritis. Patients with benign prostatic hypertrophy may develop acute urinary retention when hospitalized for an acute illness. Longstanding diabetes could result in a neurogenic bladder, which could also contribute to urinary retention. The absence of red cells and red cell casts in the urinary sediment make post-infectious glomerulonephritis due to the patient's pneumonia unlikely.
The initial management of the patient should be antibiotics for pneumonia, hydration and a kidney ultrasound with a bladder residual volume. Ultrasonography before and after voiding provides a noninvasive way of determining if the patient can empty his bladder without inserting a Foley catheter. A post-void residual bladder volume greater than 75 mL is abnormal. It is important to determine if the patient is able to empty his bladder because medical treatment with an α-blocker could prevent complete urinary retention.
The most important information at the time of admission is prior laboratory and ultrasound results. Every effort should be made to call the prior treating physicians to obtain previous BUN and creatinine results. If the BUN and creatinine were previously normal, the patient has acute renal failure, which is potentially reversible. Past BUN and creatinine results that were in the same range as the admission blood tests indicate that the patient has chronic renal failure. If a recent outpatient kidney ultrasound was performed and the serum creatinine was the same as on past tests, it would not be necessary to reorder an ultrasound on this admission.
Should a nephrology consultation be obtained on this admission?
A nephrology consultation during this admission could contribute to the patient's care in several ways. A nephrologist could help the hospitalist improve the patient's renal function and recommend strategies to delay the progression of chronic renal failure. In the case of our patient, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers to delay progressive renal failure should be considered when he is back at his baseline renal function. Controlling blood pressure to low-normal levels, controlling blood sugar, and decreasing elevated serum cholesterol and LDL levels are also important goals in preserving renal function. Cigarette smoking is an independent risk factor for developing end-stage renal failure because it increases renal artery atherosclerosis. Smoking cessation should be addressed during this admission. Comanagement of the patient with the nephrologist will help the patient continue to work toward these goals when he leaves the hospital and is followed as an outpatient.
The main reason to obtain a nephrology consultation is to prevent late referral of patients for renal replacement therapy. One third of patients with advanced chronic renal failure continue to have late referral for dialysis and transplantation, and late referral occurs in multiple countries (Am J Kidney Dis. 2005;46:881-886). Late referral results in a greater chance of an unplanned initiation of dialysis, less access to renal transplantation and peritoneal dialysis, and worse long-term survival. Diabetic patients and black patients, especially black men, have worse survival when referred late. Early referral to the nephrologist is associated with decreased use of dialysis catheters as access, lower morbidity, shorter hospital stays, improved rehabilitation, and lower treatment costs (Am J Kidney Dis. 1998; 31:398-417). Although nephrologists have attempted for more than a decade to have primary care physicians refer patients early, early referral rates have not improved.
Our patient's admission for pneumonia represents an opportunity for the hospitalist to improve his renal function and delay the progression of chronic renal failure. It is also an opportunity to make sure that the patient is followed by the nephrologist and is properly prepared for the renal replacement therapy of his choice. A telephone call to the patient's nephrologist will help the hospitalist decide if the patient is at risk for late referral for renal replacement therapy. If the patient has been lost to follow-up, a nephrology consultation will allow the patient to reconnect with the nephrology team, become educated about chronic renal failure, and schedule future care.