Simplified Bladder Measurement Identifies Postoperative Urinary Retention

A simple ultrasound (US) test can accurately diagnose the common problem of postoperative urinary retention (POUR), according to a new study.

Researchers at Lapeyronie University Hospital (Montpelier, France) conducted a study to determine whether a simplified US measurement of just the largest transverse diameter of the bladder could be used to diagnose urinary retention. One hundred patients at risk for POUR following orthopedic surgery were evaluated in the postanesthesia care unit before discharge. Bladder diameter was first measured using a portable ultrasound device; an automated evaluation of bladder volume was then performed. Finally, when bladder catheterization was performed, the actual urinary volume was measured (in 49 patients).

The researchers examined correlations between bladder volumes and diameter with receiver operating characteristic curves constructed to determine performance in predicting a bladder volume of over 600 mL. They found a significant correlation between the largest transverse diameter and urinary volumes, as assessed by the other two methods. The average bladder diameter was about 11 cm in patients with POUR, compared with 8–9 cm in those without POUR. The researchers determined that if the bladder diameter was 9.7 cm or less, the patient could be safely discharged.

If the diameter was larger than 10.7 cm, POUR might be present and catheter placement should be considered. The US test would be considered inconclusive only for patients in the "grey zone," i.e., between 9.7 and 10.7 cm. According to the researchers, the simplified measurement method could replace expensive bladder volume measuring devices or more complex US procedures involving the measurement of bladder diameters in three axial dimensions. The study was published on January 30, 2015, in Anesthesia & Analgesia.

“The findings of this study directly call into question the usefulness of expensive specific devices for assessing POUR in the postoperative period,” concluded lead author Aurélien Daurat, MD, and colleagues of the department of anesthesia and critical care medicine. “The test can be efficiently performed by nurses using a widely available portable ultrasound device, an important advantage over approaches using more complex measurements or specialized equipment.”

POUR is defined as the inability to void with a full bladder. The incidence of urinary retention after anesthesia and surgery ranges between 5% and 70%, depending on the type of surgery and the criteria used to define urinary retention. For the patient, retention of urine is painful and requires decompression of the urinary bladder using an intermittent or indwelling urethral catheter, although suprapubic catheterization may be considered if there is urethral trauma or stenosis. A problem arises, however, since catheterization is associated with risks, and an estimated 80% of hospital-acquired urinary tract infections are caused by indwelling urethral catheters.

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Lapeyronie University Hospital