Situation: A 45-year-old man is on day 5 after a living-donor kidney transplant. He takes tacrolimus at 8:00 AM and 8:00 PM, mycophenolate, and prednisone. He has an indwelling urinary catheter, and his urine output over the past day was 150–200 mL/h. Over the last 2 hours, his urine output has fallen to 20 mL/h. His blood pressure is 132/84 mmHg, and he has no pain. What should the nurse do FIRST?

A sudden drop in urine output after kidney transplant may come from graft thrombosis, obstruction, or rejection, but the quickest correctable cause is a blocked catheter. The nurse first checks the catheter and tubing for clots or kinks, then reports at once. Raising fluids without an order or waiting for laboratory results delays finding the cause.

Clinical context
A sudden drop in urine output during the early post-transplant period is a nursing priority because the new kidney is vulnerable to graft-threatening events such as vascular thrombosis, acute rejection, or mechanical obstruction ^[1][2][3][4]. On day 5 after living-donor transplantation, the patient had been making 150–200 mL/h, so a fall to 20 mL/h over 2 hours represents an abrupt and significant change.

Why the catheter is checked first
The most rapidly correctable cause of sudden oliguria in a transplant recipient with an indwelling urinary catheter is mechanical obstruction of the drainage system. A kinked tube, a dependent loop, sediment, or a clot can block outflow and mimic a dangerous drop in urine production. Because catheter obstruction can be identified and relieved at the bedside within seconds, it must be ruled out before more invasive or time-consuming steps are taken. The patient’s stable blood pressure of 132/84 mmHg and absence of pain make hypovolemia or acute surgical bleeding less likely as the immediate explanation, which further supports checking the tubing before escalating care.

Differential causes of early post-transplant oliguria

Cause	Key feature	First nursing action
Catheter obstruction	Sudden drop in output, bladder may be distended, no hemodynamic change	Inspect catheter and tubing for kinks, clots, or dependent loops; flush only with an order
Vascular thrombosis	Abrupt anuria, graft tenderness, rising creatinine; may occur in first month	Notify transplant team immediately after checking the catheter
Acute rejection	Gradual or sudden decline in output, fever, graft swelling, elevated creatinine	Report findings; prepare for labs and possible biopsy
Hypovolemia or hypotension	Low blood pressure, tachycardia, poor skin turgor, recent high output	Assess volume status; do not increase IV fluids without an order

Why the other options are not first
Watch out! Notifying the transplant surgeon is essential, but it should occur after the nurse has gathered the immediate bedside information. A call that includes “the catheter is patent and there are no kinks” is far more useful than a call that skips this step. Key point! Increasing the intravenous fluid rate without a specific order is unsafe in a transplant recipient because fluid overload can worsen graft function and precipitate pulmonary edema, especially when the cause of oliguria is not yet known. Sending blood for an urgent serum creatinine is appropriate, but it takes time to result and does not address a mechanical obstruction that could be fixed immediately.

Pathophysiology link to graft vulnerability
Early allograft function depends on adequate renal perfusion and unobstructed urine drainage. Perioperative factors such as hemodynamic instability, vascular compromise, and surgical complications can all reduce urine output in the first days to weeks ^[1]. Renal vein thrombosis, although uncommon, is a feared early complication that can lead to rapid graft loss if not recognized promptly ^[2]. Renal artery thrombosis similarly threatens the graft and may be related to technical factors or hypercoagulable states ^[3][4]. A blocked catheter is the least dangerous of these possibilities and the easiest to correct, which is why it is assessed first in the nursing sequence.

Clinical reasoning summary
The nurse’s first action is to inspect the catheter and tubing for clots or kinks. If the system is patent and the oliguria persists, the nurse then notifies the transplant surgeon immediately, prepares to send urgent labs including serum creatinine, and continues close monitoring of vital signs, urine output, and graft site. This sequence prevents unnecessary delays in identifying a correctable mechanical problem while still ensuring rapid escalation for true graft-threatening events.