A 58-year-old woman with no prior abdominal surgery presents with acute severe abdominal pain, nausea, and vomiting. On examination, she is in distress with a palpable abdominal mass in the right lower quadrant. Plain abdominal X-ray shows dilated small bowel loops and a large-diameter colon (8 cm) with a "bird's beak" appearance at the hepatic flexure on CT. There is no free perforation. What is the most likely diagnosis?

Explanation

## Diagnosis: Caecal Volvulus ### Clinical Presentation **Key Point:** Acute onset pain with a palpable abdominal mass in the right lower quadrant, combined with imaging showing a dilated colon with a "bird's beak" transition point at the hepatic flexure, is diagnostic of caecal volvulus. ### Pathophysiology Caecal volvulus occurs when the caecum and ascending colon twist on their mesentery, creating a closed-loop obstruction. The twist typically occurs in an **axial** (around the long axis) or **anterior** (caecum flips anteriorly) pattern. The "bird's beak" sign represents the point of torsion where the mesentery is twisted. ### Imaging Features: Volvulus vs. Other Causes | Feature | Caecal Volvulus | Sigmoid Volvulus | Ogilvie's | Toxic Megacolon | |---------|-----------------|------------------|-----------|------------------| | **Location of dilation** | Caecum + ascending colon | Sigmoid colon | Entire colon | Transverse/descending colon | | **Transition point** | Hepatic flexure (bird's beak) | Sigmoid (twisted loop) | Gradual, no transition | Gradual, no transition | | **Appearance** | Dilated caecum with twist | Omega or "coffee bean" loop | Smooth, featureless dilation | Dilated with haustra loss | | **Associated findings** | Small bowel dilation (closed loop) | Minimal small bowel dilation | Recent surgery/immobility | Fever, toxic appearance, bloody diarrhea | | **Age group** | Younger (30–50 yrs) | Older (>60 yrs), institutionalized | Post-operative | IBD patients | **High-Yield:** The **"bird's beak"** sign is pathognomonic for caecal volvulus — it represents the twisted mesentery at the point of torsion, typically at the hepatic flexure. ### Why This Is Caecal Volvulus 1. **Acute presentation with palpable mass** — suggests a closed-loop obstruction with a focal anatomical abnormality (the twisted caecum). 2. **Right lower quadrant mass** — the twisted caecum is palpable in the RLQ. 3. **Bird's beak at hepatic flexure** — pathognomonic for caecal volvulus; the caecum twists and the torsion point is at the hepatic flexure. 4. **No prior surgery** — excludes adhesions; volvulus is a primary anatomical twist, not secondary to scarring. 5. **Dilated small bowel** — indicates closed-loop obstruction; the twisted caecum acts as a one-way valve, trapping proximal bowel. ### Management Algorithm ```mermaid flowchart TD A[Caecal volvulus suspected]:::outcome --> B{Signs of perforation or ischemia?}:::decision B -->|Yes: Free air, wall enhancement loss, pneumatosis| C[Emergency surgery]:::urgent B -->|No: Intact wall, normal enhancement| D{Attempt endoscopic reduction?}:::decision D -->|Possible: Accessible twist| E[Colonoscopic detorsion]:::action D -->|Not possible: High twist, inaccessible| F[Surgical detorsion ± cecopexy]:::action E --> G{Success?}:::decision G -->|Yes| H[Elective surgery in 2-4 weeks]:::action G -->|No| F C --> I[Resection if ischemic]:::action ``` **Clinical Pearl:** Unlike sigmoid volvulus (which can often be decompressed endoscopically), caecal volvulus is usually managed surgically because the twist is typically not accessible to the colonoscope. Cecopexy (fixation of the caecum to the peritoneum) or right hemicolectomy is the definitive treatment. **Mnemonic:** **BIRD'S BEAK** = **B**owel twist at **I**leo-caecal region, **R**ight-sided **D**ilation, **S**udden onset, **B**eaked appearance at **E**xit point, **A**cute **K**losed-loop obstruction.