Case in Point: Bladder Knots

The patient was a 6-year-old boy who had Menkes syndrome and bladder diverticula. He was receiving care at home with sterile intermittent catheterization.

On the night of presentation, an 8F feeding tube had been inserted approximately 30 cm to effect urinary drainage. The patient was transferred to our facility after attempts to withdraw the catheter were unsuccessful.

In the emergency department, the child was afebrile and had stable vital signs. He was comfortable and in no acute distress. His abdomen was soft and nontender; however, bladder distention was evident on palpation. With gentle suprapubic pressure, the patient was able to release some urine around the catheter.

Abdominal plain films revealed a catheter coiled in a complex manner in the pelvis (Figure). The interventional radiology service successfully removed the catheter using a guidewire under fluoroscopy.

The potential for flexible tubes and wires to become knotted when introduced a sufficient length into the bladder has been recognized since the first case series was reported in 1974.¹ Before then, knotting was not a recognized complication of bladder catheterization. Two years later, this complication was first reported following standard transurethral bladder catheterization.² There have since been an additional 27 reports of "bladder knots" following transurethral catheterization.^3-21 There have also been a handful of reports related to bladder knots formed in the setting of percutaneous cystostomy drainage and urinary stoma catheterization.^22,23

Bladder knots following transurethral catheterization occur almost exclusively in young boys who have been catheterized with a feeding tube. The softer, more flexible feeding catheters often used in pediatric patients--and the tendency to overestimate the length of the male urethra--may increase the likelihood of coiling and knotting as the bladder decompresses around the coiled tubing. Authors reporting this complication previously have recommended using a less flexible dedicated urinary catheter and also limiting the depth of insertion either until urine flows or based on age and sex-based standards of insertion length.^{13,15,16,20,21}

Despite this information, bladder knots continue to occur. This suggests the need to continue to raise awareness of this preventable complication.

Two relatively recent advancements have the potential to decrease the risk of bladder knots. Ambroz and Eilber²⁴ reported that negative pressure bladder catheterization using a syringe attached to a feeding tube did not result in hematuria. This technique allows for more rapid visualization of urine obtained, and it might be less likely to lead to overzealous advancement of the urinary catheter when a feeding tube is used.

Chen and colleagues²⁵ reported that bedside bladder ultrasonography increases the likelihood of successful catheterization. It is currently impractical to consider this technology in all cases of bladder catheterization. When it is available, however, it might be a consideration in certain patients--such as those in whom advancement of the catheter as far as the acceptable standards has not yielded urine. Verification of the presence of obtainable urine in the bladder before advancing further might also decrease the risk of excessive vesical catheter length resulting from blind "exploratory" advancement.