Answer
Reading File
Finding Sources
The answer is D. Sigmoid volvulus.
Radiological Analysis
The X-ray shows the classic "coffee bean sign" (also called the "bent inner tube sign") — a massively dilated loop of colon forming a large, inverted U-shaped gas shadow that fills the entire abdomen, with a central white line (the apposed walls of the twisted loop) running diagonally from the left iliac fossa toward the right upper quadrant.
Key findings on this film:
| Feature | What it means |
|---|---|
| Massively distended single loop filling the abdomen | Closed-loop obstruction |
| Coffee bean / bent inner tube shape | Sigmoid colon twisted on its mesentery |
| Apex pointing toward right upper quadrant | Classic orientation of sigmoid volvulus |
| Central dense white stripe | Apposed, edematous walls of the two limbs of the twisted loop |
| No haustra visible in the dilated loop | Confirms colonic (not small bowel) origin |
| Loss of rectal gas | Obstruction at the rectosigmoid level |
Why not the other choices?
| Option | Why excluded |
|---|---|
| A. Small bowel obstruction | SBO shows multiple dilated loops with valvulae conniventes (herringbone), centrally located — not a single dominant loop |
| B. Intussusception | Typically seen in children; X-ray may show a soft tissue mass or leading edge, not a massively dilated single loop |
| C. Paralytic ileus | Causes diffuse, generalized gas throughout both small and large bowel with no transition point — not a single dominant loop |
Clinical Pearl
Sigmoid volvulus accounts for ~60–75% of all colonic volvuli. The coffee bean sign on plain AXR has a sensitivity of ~57–80% and is highly specific when present. CT confirms and shows the "whirl sign" (twisted mesentery). Initial management is endoscopic decompression (rigid or flexible sigmoidoscopy) unless peritonitis is present, in which case emergency surgery is required.
Answer: D — Sigmoid volvulus ✓
Answer
This is a PA (posteroanterior) chest X-ray with labelled anatomical structures. Here are the identifications:
Labelled Structures
| Label | Structure | Notes |
|---|---|---|
| a | Right hilum | Where the right main bronchus, pulmonary artery, and veins converge; normally the left hilum sits slightly higher |
| b | Right heart border (right atrium) | Forms the right cardiac silhouette on PA CXR |
| c | Right lower lobe / right costophrenic angle region | Lung parenchyma of the right lower lobe |
| d | Right hemidiaphragm | Normally higher than the left due to the liver underneath |
| e | Trachea / carina | Midline air column; the carina is the bifurcation point at the angle of Louis (T4/T5) |
| f | Left hilum | Left pulmonary artery and bronchus; typically 0.5–1.5 cm higher than the right |
| g | Left heart border (left ventricle) | Forms the left lower cardiac silhouette |
| h | Left lower lobe | Lung parenchyma of the left lower lobe |
| i | Left hemidiaphragm | Typically lower than the right; gastric bubble often visible beneath it |
| j | Gastric air bubble / left upper abdomen | Air in the fundus of the stomach below the left hemidiaphragm |
Key Observations on This Film
- Trachea (e) is midline — no mediastinal shift
- Hila (a, f) are at appropriate levels with the left slightly higher — normal
- Cardiac silhouette has a normal cardiothoracic ratio (< 0.5)
- Both hemidiaphragms (d, i) are well-defined, with the right appropriately higher
- Lung fields appear clear bilaterally — no obvious consolidation, effusion, or pneumothorax
- Costophrenic angles are sharp — no effusion
This is a normal PA chest X-ray.
Why is a not superior vena cava
Great challenge — you may well be right. Let me reconsider.
Re-examining Label "a"
Looking at the image again, label a points to the right side of the mediastinum, at approximately the level of the 2nd–3rd anterior intercostal space, running along the right paratracheal border.
That is precisely the location of the Superior Vena Cava (SVC).
SVC vs Right Hilum — How to Distinguish
| Feature | SVC | Right Hilum |
|---|---|---|
| Location | Right paratracheal, upper-mid mediastinum | Lower, at the level of the anterior end of the right 6th rib |
| Level on CXR | ~T2–T4 (upper mediastinal border) | ~T5–T6 |
| Border it forms | Right upper mediastinal border | Right mid-mediastinal "bulge" |
| Shape | Smooth, straight vertical line | Convergence of vessels — slightly lobulated |
Verdict
You are correct. Label a is more accurately the Superior Vena Cava (SVC), forming the right upper mediastinal border. The right hilum would be slightly lower and more lateral than where label a points.
Apologies for the initial misidentification. Good anatomical eye.
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