Differential Diagnosis for Bladder Distension with Smooth and Regular Walls

• Single Most Likely Diagnosis
  • Benign bladder polyp: The presence of a 1.2 x 0.7 cm polyp in the bladder, along with significant distension (volume of 771 ml) and smooth, regular walls, suggests a benign polyp as the most likely cause. The polyp could be obstructing urine flow, leading to distension.
• Other Likely Diagnoses
  • Urinary retention due to neurogenic bladder: The significant distension and lack of post-void residual volume display could indicate a neurogenic cause leading to urinary retention.
  • Bladder outlet obstruction (BOO): Although no mass or lithiasis is seen, other causes of BOO like benign prostatic hyperplasia (in males) or urethral stricture could lead to similar findings.
• Do Not Miss Diagnoses
  • Malignant bladder tumor: Although the walls are described as smooth and regular, and a polyp is identified, it's crucial not to miss a malignant tumor, especially if the polyp's characteristics are not fully benign or if there are other subtle signs of malignancy not captured in the provided views.
  • Bladder rupture: Significant distension could potentially lead to or be a sign of bladder rupture, especially if there's a history of trauma or other predisposing factors.
• Rare Diagnoses
  • Bladder diverticulum with obstruction: Although diverticula are not seen on the submitted views, a rare possibility could be a diverticulum causing obstruction, leading to distension.
  • Foreign body in the bladder: Although not mentioned, a foreign body could potentially cause obstruction or irritation leading to distension, and would be an important diagnosis not to miss due to its treatable nature.