A bowel obstruction can be either mechanical or functional, affecting the small or large intestines. It occurs when the bowel lumen becomes partially or completely blocked. The most frequent causes of large-bowel obstruction include malignancy, inflammatory strictures from diverticular disease, and sigmoid or caecal volvulus. The prognosis for large-bowel obstruction is generally favorable if diagnosed and treated early; however, if the obstruction is identified late, left undiagnosed, or if the patient is not properly resuscitated before surgery, morbidity and mortality rates can be high. Therefore, it is crucial to consider less common causes of intestinal obstruction when making a differential diagnosis. Extrinsic obstruction caused by urinary bladder distension is rare, with only a few reported cases in the last 25 years [1].

The bladder is a hollow, muscular organ responsible for storing and expelling urine. Under normal conditions, it can hold about 350 to 400 mL of urine. The lower urinary tract and distal colon share a common embryological origin, resulting in a close anatomical and functional connection. It has been noted that abnormalities in one system can potentially impact the other [2]. While conditions involving both systems, such as dysfunctional elimination syndrome, have been documented, no cases of colonic obstruction caused by urinary system pathology have been reported in children. In adults, however, only a few instances exist. MacGiobuin et al. described a case involving a 72-year-old man with colonic obstruction due to urinary retention secondary to benign prostatic hyperplasia [3]. Another study reported two elderly patients experiencing intestinal obstruction linked to urinary retention [4]. In addition to the compressive effect of a distended bladder, constipation may be exacerbated by the rectovesicourethral reflex. Buntzen et al. [5] demonstrated that as bladder distention increased, anal pressure significantly rose, while rectal motility ceased. This was attributed to the excitatory "vesico-anal" reflex, mediated at the spinal cord level.

Due to the limited space within the pelvis, bladder distension can exert pressure on nearby structures. It has been observed to compress the inferior vena cava [6] as well as the right and left external iliac veins [7]. In some cases, this compression has resulted in the formation of deep vein thrombosis [7]. Hopkins et al. [8] reported elevated pressures in the femoral veins, particularly in cases of urinary retention where bladder capacities exceeded 1000 mL. Patients with leg edema were found to have the highest femoral vein pressures. Similarly, a distended bladder can compress the recto-sigmoid colon, as seen in our patient.

Acute or acute-on-chronic urinary retention is a common surgical condition, especially in elderly men. It is primarily diagnosed clinically, presenting with lower abdominal discomfort, an inability to pass urine, and a palpable pelvic mass that is dull on percussion [9]. In rare cases, diagnosis may be challenging due to a co-existing distended abdomen. Similarly, intestinal obstruction is primarily a clinical diagnosis, supported by radiological investigations [10]. Acute urinary retention can arise secondary to various acute abdominal conditions, including diverticulitis, perforated or ischemic bowel, or an abdominal aortic aneurysm [10]. An episode of acute urinary retention, particularly when associated with elevated blood urea levels, may result in intestinal pseudo-obstruction and ileus [10]. However, urinary retention is rarely reported as a direct cause of mechanical intestinal obstruction.

The initial diagnosis of intestinal obstruction often relies on plain abdominal X-rays, which reveal distended bowel loops and collapsed segments distal to the obstruction. Water-soluble enemas, with sensitivities and specificities of 96% and 98%, respectively, are more effective for diagnosing colonic obstruction. CT imaging, increasingly used for suspected small bowel obstruction, offers 100% sensitivity and specificity, making it the preferred method for determining the obstruction's level, cause, severity, and complications like strangulation, guiding surgical management [11,12].