**Core Concept**
Haemorrhoidectomy is a surgical procedure to remove haemorrhoids, which are swollen veins in the anal canal. The procedure can cause temporary damage to the surrounding nerves and tissues, leading to complications.

**Why the Correct Answer is Right**
Urinary retention is a common complication following haemorrhoidectomy due to the proximity of the anal sphincter to the urethra. During the procedure, the anal sphincter is stretched, which can put pressure on the urethra and cause temporary urinary retention. This is often seen in patients with pre-existing urinary retention or those who have undergone previous anal surgeries. The use of general anesthesia and postoperative pain can also contribute to urinary retention.

**Why Each Wrong Option is Incorrect**
**Option A:** Hemorrhage is a possible complication of haemorrhoidectomy, but it is not the most common one. Hemorrhage can occur due to ligation of the haemorrhoidal arteries or as a result of the surgical procedure itself.

**Option B:** Infection is a potential complication of any surgical procedure, but it is relatively rare following haemorrhoidectomy. The risk of infection can be minimized with proper wound care and antibiotic prophylaxis.

**Option C:** Fecal impaction is not a direct complication of haemorrhoidectomy. However, patients may experience constipation or difficulty passing stools in the postoperative period due to pain or changes in bowel habits.

**Clinical Pearl / High-Yield Fact**
It is essential to counsel patients undergoing haemorrhoidectomy about the risk of urinary retention and to instruct them on how to manage this complication, such as performing pelvic floor exercises and using a catheter if necessary.

**Correct Answer:**
✓ Correct Answer: D. Urinary Retention