8
Large Bowel
Diverticular Diseases
Overview
Diverticula are outpouchings of the mucosa through the colonic wall. Usually located at the area of colonic wall that is traversed by arterioles (vasa recta)
False diverticulum includes only mucosa and submucosa
May lead to perforation or bleeding
Signs and Symptoms
Abdominal pain, fever, leukocytosis, lower GI bleeding
Diagnosis
Hinchey classification of perforated diverticular disease:
• Class I: Perforation with localized paracolonic abscess
• Class II: Perforation with pelvic abscess
• Class III: Perforation with purulent peritonitis
• Class IV: Perforation with feculent peritonitis
Diverticulitis: CT scan with IV contrast. Water-soluble rectal contrast is relatively contraindicated in the setting of acute diverticulitis
Lower GI bleed from diverticula: Colonoscopy, visceral angiography, tagged red blood cell scan
Treatment/Management
Diverticulitis with no diffuse peritonitis: Conservative treatment with bowel rest, antibiotics
Recurrent diverticulitis: Cut off for timing of surgery still a controversial debate, but most patients are offered resection if they have had more than three episodes of diverticulitis;failure to resolve an episode despite medical management; complicated diverticulitis (for example: perforation with abscess formation, colovesicular fistula, etc); or if the attacks are increasing in severity or frequency
Abscess: IR drainage
Bleeding: Resuscitation, therapeutic colonoscopy, IR embolization, surgical resection for persistent, or the rare case of uncontrollable bleeding
RADIOLOGY
Diverticulosis
CT findings (Fig. 8.1)
• Focal outpouchings from the colonic wall without surrounding inflammation (which would indicate diverticulitis)
FIGURE 8.1 A–E
A. Psoas muscle
B. Vertebra
C. Small bowel loops
D. Liver
E. Stomach
F. Spleen
G. Descending aorta
H. Bladder
FIGURE 8.1 A
FIGURE 8.1 B
FIGURE 8.1 C
FIGURE 8.1 D
FIGURE 8.1 E
Diverticulitis
Plain film findings
• Usually normal, but may see thickened loops of colon
US findings
• May reveal a pericolic abscess as a hypoechoic fluid collection with posterior acoustic enhancement near the bowel wall, surrounded by inflamed hyperechoic fat
CT findings (Fig. 8.2)
• Pericolonic fat stranding and edema
• May see a loculated, rim enhancing fluid collection, representing an abscess
• Colonic wall thickening secondary to inflammation
• Mild disease is characterized by minimal wall thickening and pericolonic inflammatory changes
• Moderate disease is characterized by the formation of pericolonic fluid collections, representing abscesses
• Severe disease is characterized by marked wall thickening, large amount of free air, large fluid collections, or marked phlegmonous changes
FIGURE 8.2 A,B
FIGURE 8.2 A
FIGURE 8.2 B
Perforated Diverticulitis
CT findings (Fig. 8.3)
• Free intraperitoneal air
• Pericolonic fat stranding surrounding the perforated diverticuli
FIGURE 8.3 A–D
A. Psoas muscle
B. Vertebra
C. Small bowel loops
D. Liver
E. Stomach
F. Bladder
G. Kidney
FIGURE 8.3 A
FIGURE 8.3 B
FIGURE 8.3 C
FIGURE 8.3 D
Diverticular Pelvic Abscess
CT findings (Fig. 8.4)
• Loculated, rim-enhancing fluid collection around the site of diverticulitis
• Extensive surrounding fat stranding
FIGURE 8.4 A–C
A. Sacrum
B. Ilium
C. Fat stranding
D. Liver
E. Small bowel loops
F. Bladder
G. Descending aorta
H. IVC
I. Portal vein
J. Vertebra
K. Uterus
FIGURE 8.4 A
FIGURE 8.4 B
FIGURE 8.4 C
Colovesicular Fistula
RADIOLOGY
CT findings (Fig. 8.5)
• Gas within the bladder
• Focal wall thickening of the bladder
• Tethering of the colon to the bladder is usually seen. The fistula tract is usually not seen on CT
FIGURE 8.5 A–C
A. Rectum
B. Femoral head
C. Liver
D. Stomach
E. Small bowel loops
F. Urinary bladder
G. Superior mesenteric vein
H. Descending aorta
I. Vertebra
FIGURE 8.5 A
FIGURE 8.5 B
FIGURE 8.5 C
Colorectal Cancer
Hereditary colorectal cancer syndromes
• Make up 5% to 10% of all colorectal cancers
• Autosomal dominant
Hereditary nonpolyposis colorectal cancer (HNPCC) also known as Lynch syndrome
• Most common inherited colorectal cancer (2% to 4% colorectal cancers)
• Amsterdam criteria
Three relatives with histologically proven colorectal CA (one first degree)
Two successive generations
One diagnosed prior to the age of 50 years
• DNA mismatch repair
• 50% to 85% lifetime risk of colon cancer
• Extracolonic manifestation: Tumors of endometrium, ovaries, stomach, small bowel, hepatobiliary tract, pancreas, ureter, renal pelvis
Familial adenomatous polyposis (FAP)
• Second most common familial colorectal cancer
• Hundreds to thousands of adenomatous polyps
• APC gene mutation chromosome 5
• Almost all patients will develop colon cancer
• Mean age polyposis at 15 years of age
• Extracolonic manifestation: Duodenal polyps (periampullary cancer), desmoid tumors, epidermoid cyst, mandibular osteomas (Gardner’s syndrome), central nervous system tumors (Turcot syndrome)
Attenuated FAP
• Fewer polyps
• Later age onset (30 years)
• 70% lifetime risk for colon cancer
Peutz–Jeghers syndrome
• Hamartomatous polyps
• Polyps of small intestine, rectum, colon
• Melanin spots in buccal surface
Juvenile polyposis syndrome
• Hamartomatous polyps
• Hundreds of polyps in rectum or colon
• May degenerate into adenoma and carcinoma
Diagnosis
Screening
• For average risk start screening at the age of 50 years
• More frequent screening if history of polyps, colon cancer, inflammatory bowel disease, family history of colon cancer
Preoperative evaluation
• CT chest, abdomen, pelvis
• Colonoscopy (synchronous tumors ∼5%)
• Rectal cancer—endorectal ultrasound
• CEA level
Treatment/Management
Resection
Twelve lymph nodes required for adequate staging
± adjuvant chemotherapy
RADIOLOGY
Colon Cancer
Plain film/contrast enema findings
• Annular cancers manifest as shouldering with an irregular narrow lumen
• Polypoid cancers usually present as intraluminal masses that protrude from the wall into the lumen of the colon
• Obstruction is much more common on the left due to its smaller caliber compared to the right hemicolon
CT findings (Fig. 8.6)
• Enhancement of cancer
• Heterogeneous enhancement with abscess formation (secondary to perforation)
• Calcification may be seen with mucinous adenocarcinomas
• Infiltration into the surrounding pericolonic fat can indicate extension of tumor outside of the colonic serosa and local invasion
• Retroperitoneal lymph nodes or pelvic nodes greater than 1 cm in the short axis, or clusters of intra-abdominal nodes may indicate regional lymph node metastases
FIGURE 8.6 A,B
A. Psoas muscle
B. Small bowel loops
C. Vertebra
D. Liver
E. Portal vein
F. Right common iliac artery
G. Stomach
H. Spleen
I. Bladder
FIGURE 8.6 A
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