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DMD Nephrology Case 1 – Acute Renal Failure

 

You are requested to see an 80-year-old man on the surgical service because of an elevated BUN and creatinine. He had just undergone a splenectomy for thrombocytopenia secondary to splenomegaly from underlying chronic lymphocytic leukemia.  Immediately before surgery his BUN was 22 mg/dl, creatinine was 1.3 mg/dl, urinalysis was normal.  When checked two days post operatively, his BUN had increased to 40mg/dl, and creatinine was 3/0 mg/dl.  Urine output for each of the last two days was approximately 250 ml/day.

 

Discussion points:

  • Given the above information, how would you characterize this patient’s kidney problem? (Go through the differential of prerenal, renal and post renal causes of azotemia)
  • What further information do you need to get historically, through the hospital record, and on physical exam on assessing this patient’s problems?

 

The patient denies symptoms of congestive heart failure.  He has not been extremely thirsty over the last several days.  He has had difficulty urinating over the past several years with a weak urinary stream and nocturia 3-4 times per night. His doctor told him that he had BPH but no therapy was given. The patient denies leg pain or flank pain.  The hospital chart is reviewed which showed the patient had significant bleeding in the operative period with several episodes of hypotension with systolic blood pressure in the 80 range.  These episodes lasted for short periods of time less than 5 minutes and returned to normal blood pressure after that period.  His urine output was 700 ml/day immediately after surgery and dropped to 200-300 ml/day over the past two days.  For the three days after surgery his total fluid balance is positive 3 liters.  His only medication postoperatively was analgesia with Dilaudid.  He did receive one dose of Cephalothin preoperatively and none since that time.

 

Discussion point:

  • How does this historical information affect your differential? (Include possibilities of post-obstructive renal failure secondary to prostatism, and acute tubular injury secondary to hypotensive episodes.)

 

The patient’s physical exam showed his T-37 C, RR-14, BP-130/90, P-82 with no orthostatic changes.  His mucous membranes were moist.  Neck pains were 1cm above the sternal angle.  The patient’s lung exam was clear to auscultation and percussion without rales.  Cardiac exam has a normal S1, S2 without S3 or murmurs appreciated.  The patient’s abdomen was soft with slight tenderness over the surgical scar.  No ecchymosis were noted.  The patient had no CVA tenderness or ecchymosis present in the back.  A foley catheter was placed in the patient at that time which showed approximately 50 cc of urine in the patient’s bladder.

 

Discussion points:

  • How does his physical examination help you in determining the cause of this patient’s acute renal failure? (No signs or symptoms of prerenal azotemia, or post renal obstruction.  The patient could conceivably have ureteral obstructions or trauma to his ureters during surgery though both seem unlikely?
  • What laboratory tests would you order at this time?

 

A fresh specimen of the patient’s urine is examined under the microscope and showed numerous epithelial cells and brown degenerating cellular casts.  No crystals or WBC’s were noted, and only rare RBC’s were present.  The urine sodium was 40 meq/l.  Urine specific gravity was 1.01.  Repeat BUN and creatinine on the 4th day after surgery are BUN-52 mg/dl, creatinine-3.5mg/dl. Uric acid was 9.2 mg/dl.  A renal ultrasound is done, kidneys are normal in size, and no signs of obstruction are present.

 

Discussion points:

  • What is your diagnosis at this time? (ATN seems most likely secondary to the patient’s episode of  hypotension during surgery. Both physical examination and renal ultrasound confirm no signs of bladder obstruction or ureteral obstruction)
  • How would you treat the patient at this time?

 

On day 6 after surgery, the patient’s BUN is 68 mg/dl, creatinine is 4.1 mg/d.  His urinary volumes are between 300-500 ml/day.  Serum electrolytes are NA – 142 mg/dl, K-4.2 mg/dl, Cl-98 mg/dl, HCO3-23 mg/dl.  The patient is started on fluid and salt restriction but he remains oliguric. By day 8 the patient’s BUN is 85 mg/dl, creatinine is 6.3 mg/dl.

 

Discussion points:

  • Is there anything else you would do to manage the patient at this point? (When do you start dialysis on a patient? What are the signs of uremia?)
  • What is the expected course of patients with acute tubular necrosis?

On day 9, postoperatively the patient’s urine output begins to rise to one liter per day, and by day 11 it is up to 3 ½ liters per day.  The patient’s BUN is up to 92 mg/dl, creatinine is 6.9 mg/dl on day 11.

 

Discussion points:

  • Given the patient is now in the polyuric phase of ATN, how would you change his fluid and electrolyte management?

 

On day 12 the patient’s urine output begins to decrease to 1/5 liters per day.  His BUN and creatinine begin to fall.  Fluid and salt restrictions are discontinued.  The patient is discharged from the hospital on day 14 and followed up as an outpatient. His BUN and creatinine returned to normal three weeks after surgery.

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