Resident Readiness General Surgery (53 page)

Lasix and low-dose dopamine may increase urine volume, but there is no evidence that they help the kidneys “bounce back” to health.

COMPREHENSION QUESTIONS

1.
You are on night float and are called about an otherwise healthy patient who had a lysis of adhesions and small bowel resection during the day. The nurse tells you that the patient has made 20 mL of urine over the past two hours. You order a 1 L bolus after confirming that his vitals are normal and that he has no other evidence of hemodynamic instability. When you check back in an hour, you learn that the patient has only made an additional 5 mL of urine. You go to evaluate the patient. Other than a physical exam, your next step should be which of the following?

A. Check a CBC.

B. Order another 1 L bolus and reevaluate in 30 minutes.

C. Order furosemide 40 mg IV.

D. Flush the Foley.

2.
A burn patient admitted 3 weeks ago has become progressively oliguric over the past six hours. She is now making just 15 mL/h and has not responded to 2 L of crystalloid. You ordered a urine spot protein. Which result would be most consistent with kidney injury (eg, ATN)?

A. 3.2 mEq/L

B. 10 mEq/L

C. 25 mEq/L

D. 50 mEq/L

Answers

1.
A
. The patient is at low risk of hemorrhage, so an empiric 1 L bolus was a reasonable first move. But since he didn’t respond, it is important to rule out other
causes of inadequate renal perfusion. If the patient’s oliguria is due to hypovolemia, furosemide will only make it worse. While a partially clogged Foley could be the cause, it is unlikely in the setting of low but nonzero urine output for three hours. While not listed as an answer, one can also check a spot urine sodium if there is any confusion about whether this is a prerenal or intrarenal problem.

2.
D
. Less than 15 mEq/L suggests a prerenal cause (hypovolemia, stress, shock), while more than 40 mEq/L suggests kidney dysfunction.

A 55-year-old Male With Postoperative Urinary Retention

Selma Marie Siddiqui, MD
and Marie Crandall, MD, MPH

A 55-year-old male with a history of diabetes mellitus underwent an uncomplicated hemorrhoidectomy under general anesthesia. No Foley catheter was placed. In the postanesthesia care unit, he complained of pain and was given IV narcotics.

The patient is admitted for observation. Six hours postoperatively, the floor nurse calls because the patient reports the urge to void but despite numerous attempts has been unable to do so. He is hemodynamically stable and mentating well, but does have distention and tenderness to palpation in the suprapubic area.

1.
What additional history or physical examination findings would be useful in this patient? What are the most common risk factors for postoperative urinary retention (POUR)?

2.
What are the most common etiologies of POUR? Which is most likely in this patient?

3.
What is your next step?

4.
In a patient with an indwelling Foley catheter removed on postoperative day #4 who is unable to void 6 hours later, what would be the best management plan?

5.
When would it be appropriate to seek a Urology consult for POUR?

POSTOPERATIVE URINARY RETENTION

POUR is a common complication resulting in numerous pages to the PGY-1 on service. The process of socially appropriate voiding requires frontal cortex coordination with the pontine micturition center to control the spinal reflex arcs manipulating the delicate balance between the promicturition parasympathetic drive and the antimicturition sympathetic drive. The desire to void should normally present with 150 cm
³
of urine, with normal bladder capacity ranging between 400 and 600 cm
³
. A clinical examination with a palpable bladder and dullness to percussion along with symptoms of lower abdominal discomfort are classic signs of POUR; however, a bedside bladder ultrasound should be obtained whenever possible to support clinical findings and estimate the degree of bladder distension.

Answers

1.
Based on common risk factors, it is possible for the astute PGY-1 to anticipate which patients are likely to suffer from POUR. Risk factors include the following:

•
BPH or prior history of POUR

•
Age 50 years or more

•
Male gender

•
Neuropathy or neurologic disorders

One can also stratify risk of POUR by type of procedure being undergone, anesthesia used, and postoperative analgesia delivered. Anorectal procedures are known for having a particularly high incidence of POUR, with studies demonstrating frequency of POUR after anorectal surgery to range between 16% and 50%, followed closely by inguinal herniorrhaphy. Spinal anesthesia, epidural anesthesia, and general anesthesia have higher incidences of POUR than local anesthesia. Opioid-based patient-controlled analgesia (PCA) has a slightly higher incidence of POUR compared with oral or IV push opioids due to the more constant inhibition of parasympathetic drives.

The duration of the procedure indirectly increases the likelihood of POUR by dose-dependent effects of anesthetic/analgesic agents. The volume of IV fluids received intraoperatively in the absence of a Foley catheter can also affect POUR as higher volumes may lead to overdistention of the bladder with possible subsequent cystopathy.

2.
Etiologies of POUR are broken down into 3 major categories:

•
Drug effect

•
Obstructive

•
Neurogenic (increased sympathetic activity)

The most common of these categories encountered in the surgical patient tends to be retention secondary to drug effects from anesthetic and narcotic agents.

In the patient presented above—a 55-year-old male with diabetes—drug effect, obstructive, and neurogenic causes are all plausible. This patient underwent general anesthesia and therefore has a high risk of a drug effect cause of his retention. BPH is the most common obstructive cause in male patients and can easily be assessed for with a digital rectal examination or review of medications taken to search for an α-blocker. Pain and anxiety, often caused by concern over being unable to void, can cause increased sympathetic tone that can further suppress micturition arcs. Furthermore, diabetes and the sequelae of neuropathies that accompany severe disease can also include diabetic cystopathy. Other neurologic disorders such as stroke, multiple sclerosis, mass effects, etc, can cause similar neurogenic bladder symptoms and can be exacerbated by stress in the postoperative state.

3.
The most appropriate next step here is to immediately obtain a bedside ultrasound estimate of intravesicular volume. Bedside bladder scanners are commonly used and a nurse can easily obtain this value. Typically, 3 scans of the bladder with an average of the 3 values are used for clinical decision making.

After obtaining a bladder ultrasound demonstrating a volume at or above normal limits (thus ruling out postoperative oliguria), it is appropriate to proceed with single intermittent catheterization. Given that this is likely a drug effect in the majority of patients, single intermittent catheterization allows the bladder to avoid damage secondary to significant distention and allows the central and peripheral nerve centers to regain function. If a patient is still unable to void an additional 6 to 8 hours later and bedside ultrasound again supports clinical evidence of a significant volume of urine in the bladder, it is appropriate to repeat intermittent catheterization.

After 2 intermittent catheterizations, if the patient is still unable to void, placement of an indwelling catheter is appropriate to prevent possible urethral trauma and overdistention of the bladder. It would also be appropriate to allow for regular intermittent catheterization if the patient or nursing staff can perform catheterization in an aseptic manner and the patient has an uncomplicated urethral tract.

In the event of urine volumes above 600 cm
³
on intermittent catheterization, there is potential for significant distention-induced dysfunction of the detrusor muscle and the patient may require bladder rest for an extended period of time. Use clinical judgment with large-volume outputs from intermittent catheterization and consider 1 or more days of bladder rest with indwelling Foley catheters before repeating a voiding trial. Patients with a history of obstructive pathology may tolerate a larger volume of distention without developing dysfunction compared with others.

4.
The appropriate next step would be to obtain a bladder ultrasound to verify a volume of urine sufficient to stimulate the micturition reflex arcs. If greater than 150 cm
³
of urine is present in the bladder, but less than 300 cm
³
, it would be appropriate to allow the patient additional time for the coordination of the multiple signals controlling physiologic micturition. If a volume of urine greater than 300 cm
³
is present on bladder ultrasound, single intermittent catheterization should be performed. If the patient is unable to void a second time with a significant bladder volume, either the patient may have an indwelling catheter placed with a plan for a repeat voiding trial subsequently or the patient can continue with aseptic intermittent catheterization until physiologic micturition function normalizes.

5.
Urology consultation may be considered when failure to void has occurred multiple times and there is unlikely to be persistent drug effect. In these patients the possibility for neurogenic or obstructive pathology must be considered and urologic evaluation is appropriate.

In a patient who presents with probable obstructive pathology causing retention, it is appropriate to initiate α-blockers (as long as the patient does not have any contraindications to this class of medications). It is appropriate to proceed with outpatient urologic evaluation for obstructive pathology that improves with α-blockers and to continue the patient on these medications postoperatively until further evaluation can be obtained.

TIPS TO REMEMBER

Bladder ultrasound is the most sensitive and specific noninvasive method for assessing intravesicular volume. If the volume exceeds 300 cm
³
, the bladder should be drained with intermittent catheterization.