Gastrointestinal SystemChapter 1

B ring (Gastroesophageal junction/ring)—commonly identified in barium swallow as thin transverse mucosal fold known as B ring.

A ring (Inferior esophageal sphincter) between 2 and 4 cm proximal to B ring, is thicker ring produced by active muscle contraction known as ring.

Phrenic ampulla(vestibule)—area between these 2 rings A and B, it corresponds with lower esophageal sphincter. It comprises physiologic 2 to 4 cm high pressure zone, which is tightly closed during resting state and assumes bulbous configuration with swallowing.

3Z line—the change from squamous epithelium of esophagus to columnar epithelium of stomach in distal esophagus is marked by irregular line called as Z line. Here straight esophageal folds ends abruptly to give rise to gastric rugae.

In case of baretts esophagus (i.e. esophagus lined by columnar epithelium) this line may lie some distance above gastro-esophageal junction. Normally Z line lies at gastro-esophageal junction.

It refers to pathological annular narrowing at B ring, causing dysphagia:

Common causes are:

When esophagogastric junction is >1.5 cm above diaphragmatic hiatus and portion of peritoneal sac forms part of wall of hernia.

When portion of stomach is superiorly displaced into thorax and esophagogastric junction remains in subdiaphragmatic position.4

Common radiological findings: These are wide, thickened folds (>3 mm) with irregular lobulated contour. Vertically oriented ulcers around 3 to 10 mm in length, mucosal erosions and nodularity, inflammatory esophagogastric polyp.

Common causes are:

Normal length—25 cm.

Normally—flattened anteroposteriorly, lumen is collapsed.

Common causes are:

Normally—1 to 2 mm wide, best seen in collapsed esophagus.

Abnormal esophageal folds—>3 mm wide with submucosal edema/inflammation.

5Common causes are:

Size of ulcer is < 1 cm.

Common causes are:

Size of ulcer is > 1 cm.

Common causes are:

Esophageal stricture—when narrowing is > 10 mm in vertical length.

Esophageal ring—refers to 5 to 10 mm (vertical length) area of complete/incomplete circumferential narrowing.

Esophageal web—refers to 1 to 2 mm thick (vertical length) area of complete/incomplete circumferential narrowing.

6Common causes are:

It refers to presence of multiple 1 to 2 mm gas-filled cysts in wall of stomach and intestine.

Clinically—little or absent gastrointestinal symptoms.

USG findings—pyloric transverse diameter >13 mm with pyloric channel closed elongated pyloric canal > 15 mm in length, pyloric muscle wall thickness > 4 mm

Target sign—hypoechoic ring of hypertrophied pyloric muscle around echogenic mucosa centrally on cross-section.

Hampton line—refers to thin, straight, 1 mm lucent line, traversing the orifice of the ulcer niche (seen on profile view).7

Complete volvulus—when rotation of stomach is >180°.

Partial volvulus when rotation of stomach is <180°, without vascular compromise.

Megabulbus—refers to dilatation of duodenal bulb only.

Megaduodenum—refers to dilatation of entire C-loop

Refers to vascular compression of 3rd part of duodenum within aortomesenteric compartment.

8Normal angle between SMA and aorta—45 to 65°

Cause—narrowing of angle to 10 to 22° due to any of the following reasons:

Megaduodenum—pronounced dilatation of 1st and 2nd portion of duodenum and frequently stomach abrupt change in caliber distal to compression defect.

Clinically present as—abdominal cramping, repetitive vomiting.

Normal diameter—< 5 mm.

Origin—1 cm caudal to coeliac axis.

Supplies—transverse and descending duodenum, jejunum, ileum, large bowel to splenic flexure.

Commonly < 1 cm, round/ovoid ulcer niche.

Giant duodenal ulcer—>2 cm.

Measurement findings on USG:

Greater than three distended small bowel loops measuring >3 cm in diameter with gas-fluid levels (seen > 3–5 hours after onset of obstruction).

Jejunum—when valvulae conniventes high and frequent.

Ileum—when valvulae conniventes sparse/absent.

Common causes are:

It is the longest tubular organ in body

Normal length—550 to 600 cm (18–22 feet).

Normal vertical diameter—2.5 cm.

Abnormal—if ≥ 4 cm.

Normal range—5–7 cm.

Risk of perforation—if ≥ 9 cm.

Normal length—10 to 12 feet.

Upper jejunum—3.0 to 4.0 cm

Lower jejunum—2.5 to 3.5 cm

Normal number of folds—4 to 7 inch.

Normal fold thickness—1.7 to 2.0 mm.

Jejunum—> 7 folds/inch, > 7 mm fold height, > 2.5 mm fold thickness.

Ileum—> 4 folds/inch, > 3.5 mm fold height, > 2 mm fold thickness.

Common causes are:

It refers to acute transmural fulminant colitis with neurogenic loss of motor tone and rapid development of extensive colonic dilatation > 5.5 cm involving transverse colon.

Common causes are:

USG measurement findings:

Appendix visualized as noncompressible, blind-ending, tubular aperistaltic structure, laminated wall withtarget appearance, mural wall thickness ≥2 mm, ≥6 mm in total diameter on cross-section, pericecal/periappendiceal fluid, enlarged mesenteric lymphnodes.12

USG measurement findings:

Target sign—concentric ring of bowel, peripheral rim hypoechogenic 8 mm thick, total diameter on cross-section is > 3 cm.

It is the most common parasitic infection in world.

Length—20 to 30 cm

Width—6 mm

13Common location—jejunum > ileum > duodenum

Common age group affected—1 to 10 years

Life cycle—infection spreads from contaminated soil, eggs hatch in duodenum, larvae penetrate into lymphatics/venules, then carried to lungs, goes to alveoli, bronchialtree, later swallowed, and matures in jejunum.

Seen as 20 to 30 cm long tubular filling defects, barium-filled enteric canal is outlined within Ascaris, whirled appearance, sometimes in coiled clusters.

Clinically present as:

If bile ducts infested—leads to jaundice.

Measurement findings on USG—seen as tubular echogenic filling defect with 2 to 4 mm wide central sonolucent line within dilated common bile duct.

This is mainly applied in case of trauma to abdomen, for taking decision for surgical intervention, focused assessment with sonography for trauma (FAST).

HP score=Depth of largest fluid collection in cm + 1 point for each additional site with fluid score of ≤ 2 managed conservatively.

It refers to the the shortest distance between the posterior rectum and sacrum.14