►Dr. Ananthakrishnan: In a healthy patient, surgery often results in a several-fold increase in the secretion of cortisol to balance the unique stressors surgery places on the body.6 This patient is at increased risk for complete or partial adrenal insufficiency in the setting of both his pituitary macroadenoma as well as his previous left nephrectomy, which could have affected his left adrenal gland as well. Thus, this patient may not be able to mount the appropriate cortisol response needed to counter the stresses of surgery. His cortisol level is abnormally low for a morning value, with a relatively normal ACTH reference range of 6 to 50 pg/mL. He may have some degree of adrenal insufficiency, and thus will benefit from perioperative steroids.
►Dr. Bhatnagar: The patient was started on hydrocortisone and underwent a successful laparoscopic partial right nephrectomy. During the procedure, an estimated 2.5 L of blood was lost, with transfusion of 3 units of packed red blood cells. A surgical drain was left in the peritoneum. Postoperatively, he developed hypotension, requiring vasopressors and prolonged continuation of stress dosing of hydrocortisone. Over the next 4 days, the patient was weaned off vasopressors, and his creatinine level was noted to increase from a baseline of 1.8 mg/dL to 4.4 mg/dL.
Dr. Rifkin, how do you think about renal recovery in the patient postnephrectomy, and should we be concerned with the dramatic rise in his creatinine level?
►Dr. Rifkin: Removal of renal mass will result in an initial reduction of GFR proportional to the amount of functional renal tissue removed. However, in as early as 1 week, the residual nephrons begin to compensate through various mechanisms, such as modulation of efferent and afferent arterioles and renal tissue growth by hypertrophy and hyperplasia.7 In the acute setting, it may be difficult to distinguish an acute renal injury vs physiological GFR reduction postnephron loss, but often the initially elevated creatinine level may normalize/stabilize over time. Other markers of kidney function should concomitantly be monitored, including urine output, electrolyte/acid-base status, and urine sediment examination. In this patient, although his creatinine level may be elevated over the first few days, if his urine output remains robust and the urine sediment examination is normal, my concern for permanent kidney injury would be lessened.
►Dr. Bhatnagar: During the first 4 postoperative days the patient produced approximately 1 L of urine per day with a stable creatinine level. It is over this same time that the hydrocortisone was discontinued given improving hemodynamics. However, throughout postoperative day 5, the patient’s creatinine level acutely rose to a peak of 5.8 mg/dL. In addition, his urine output dramatically dropped to < 5 mL per hour, with blood clots noted in his Foley catheter. Dr. Rifkin, what is your differential for causing this acute change in both his creatinine level and urine output this far out from his procedure, and what might you do to help further evaluate?
►Dr. Rifkin: The most common cause of acute kidney injury in hospitalized patients is acute tubular necrosis (ATN).8 However, in this patient, who was recovering well postoperatively, was hemodynamically stable with a robust urine output, and in whom no apparent cause for ATN could be identified, other diagnoses were more likely. Considering the abrupt onset of oligo-anuria, the most likely diagnosis was urinary tract obstruction, particularly given the frank blood and blood clots that were present in the urine. Additional possibilities might be a late surgical complication or infection. Surgical complications could range from direct damage to the renal parenchyma to urinary leakage into the peritoneum from the site of anastomosis or tissue injury. Infections introduced either intraoperatively or developed postoperatively could also cause this sudden drop in urine output, though one would expect more systemic symptoms with this. Given that this patient has a surgical drain in place in the peritoneum, I would recommend testing the creatinine level in the peritoneal fluid drainage. If it is comparable to serum levels, this would argue against a urine leak, as we would expect the level to be significantly elevated in a leak. In addition, he should have imaging of the urinary tract followed by procedures to decompress the presumed obstructed urinary tract. These procedures might include either cystoscopy with ureteral stent placement or percutaneous nephrostomy, depending on the result of the imaging.
►Dr. Bhatnagar: The creatinine level obtained from the surgical drain was roughly equivalent to the serum creatinine, decreasing suspicion for a urine leak as the cause of his findings. Cystoscopy with ureteral stent placement was performed with subsequent increase in both urine output and concomitant decrease in serum creatinine.
Around this time, the patient also began to note blurry vision. Evaluation revealed difficulty with visual field confrontation in the right lower quadrant, right eye ptosis, right eye impaired adduction, absent abduction and impaired upgaze, but intact downgaze. Diplopia was present with gaze in all directions. His constellation of physical examination findings were concerning for a pathologic lesion partially involving cranial nerves II and III, with definitive involvement of cranial nerve VI, but sparing of cranial nerve IV. Repeat MRI of the brain showed hemorrhage into the sellar mass, with ongoing mass effect on the optic chiasm and extension into the sinuses (eAppendix). These findings were consistent with pituitary apoplexy. Dr. Ananthakrishnan, can you tell us more about pituitary apoplexy?
►Dr. Ananthakrishnan: Pituitary apoplexy is a clinical syndrome resulting from acute hemorrhage or infarction of the pituitary gland. It typically occurs in patients with preexisting pituitary adenomas and is characterized by the onset of headache, fever, vomiting, meningismus, decreased consciousness, and sometimes death. In addition, given the location of the pituitary gland within the sella, rapid changes in size can result in compression of cranial nerves III, IV, and VI, as well as the optic chiasm, resulting in ophthalmoplegia and visual disturbances as seen in this patient.9