Pearls

Normal Small Bowel Enhancement

Arterial Phase

Duodenum 120 +/- 5 HU
Jejunum 119 +/- 5 HU
Ileum 118 +/- 5HU

Portal Phase

Duodenum 111 +/- 4 HU
Jejunum 111 +/- 3 HU
Ileum 107 +/- 3HU

Primary Epiploic Appendagitis: Facts

caused by torsion of an epiploic appendage or spontaneous venous thrombosis of a draining appendageal vein
acute onset of abdominal pain
laboratory findings are non-contributory

Primary Epiploic Appendacitis: CT Findings

oval shaped paracolic mass with fat attenuation
thickened visceral peritoneal lining
periappendageal fat stranding
must differentiate from diverticulitis, appendicitis, omental infarction, perforation

Small Bowel Neoplasms- Facts

represent less than 5% of GI tract tumors
variable clinical presentation
often difficult to diagnose both clinically and radiologically

Adenocarcinoma of the Small Bowel-CT Appearance

diffuse infiltration of a segment of bowel
polypoid mass
constricting lesion
large ulcerating lesion

Adenocarcinoma of the Small Bowel- Facts

more common in the proximal bowel (duodenum> jejunum> ileum)
variable clinical presentation
increased frequency in certain associated conditions (i.e. crohn disease, sprue)
5 mm reconstruction interval

Target or Halo Sign: Differential Diagnosis

ulcerative colitis
crohn's disease
infectious enterocolitis
pseudomembranous colitis
ischemic colitis
radiation colitis
chronic mesenteric ischemia
graft vs. host disease

Carcinoid Tumor-CT Appearance
In one series 70% (21/30) of mesenteric carcinoids had foci of calcification within them. These calcifications were either

small, stippled calcifications
coarse, dense calcifications
diffuse calcification

Calcification and Fibrosis in Mesenteric Cacinoid Tumor Pantongrag-Brown,L et al AJR 1995;164:387-391

CT of Crohn Disease: Extent of Disease

bowel wall pathology
mesenteric disease
extra intestinal complications
gallbladder
musculoskeletal
liver

CT vs. Plain Film/Clinical Evaluation of Small Bowel Obstruction

ability to diagnose SBO (false positive/False negative studies)
accuracy of diagnosis of SBO
cause of SBO when present
time to diagnosis (hour vs. days)

The diameter of a dilated loop of small bowel on CT is 2.5cm or greater.

Pseudomembranous Colitis: CT Findings

marked mural thickening (range 3-32 mm, average of 15 mm)
low attenuation wall thickening due to mucosal and submucosal edema
oral contrast material trapped between swollen haustra (accordion sign)
ascites (present in up to 35% of cases)

Portal Venous Gas - Differential Diagnosis

bowel
vascular catheterization
diverticulitis
acute gastric dilatation
acute intestinal dilatation
peptic ulceration
post-colonoscopy
post-ERCP

Intestinal Ischemia and Infarction - Etiology

arterial disease

occlusion secondary to atherosclerosis
occlusion secondary to emboli
trauma

venous disease

due to venous thrombosis
portal hypertension
estrogen use

Ischemic Bowel Disease: CT Findings

luminal dilatation
bowel wall thickening
dilated mesenteric veins
edema in mesenteric fat
intramural gas
mesenteric or portal venous gas

Intestinal Obstruction - Etiology

adhesions (50%)
hernias (15%)
neoplasms (15%)
multiple causes (35.5%)

Small intestinal obstruction Mucha P Surg Clin NA 67;597-620, 1987

External Hernias - Types

inguinal
femoral
umbilical
obturator
incisional

Small Bowel Adenocarcinoma - Increased Incidence

familial polyposis
Gardner's syndrome
Peutz-Jeghers syndrome
Crohn's disease

Spiral CT Evaluation of Suspected Appendicitis what is the ideal protocol ?

unenhanced CT scan
oral only study
IV contrast only
oral and IV contrast

mesenteric panniculitis

non-neoplastic benign disease characterized by inflammation of the adipose tissue of the mesentery.
opatient age-average 60 (range 20-80)
presenting symptoms: abdominal discomfort (ranging from normal to severe)
- pain
- nausea
- weight loss
- fever
- palpable mass

mesenteric panniculitis-three types pathologically

diffuse mesenteric thickening and infiltration
solitary mesenteric mass
multiple mesenteric masses

mesenteric panniculitis-CT appearance

nodular mesenteric masses
inflammation of the mesentery
"dirty mesentery"

Small Bowel Pathology

amyloidosis
whipple's disease
intestinal lymphangiectasia
scleroderma

Intestinal Ischemia and Infarction - Etiology

arterial disease

occlusion secondary to atherosclerosis
occlusion secondary to emboli
trauma

venous disease

due to venous thrombosis
portal hypertension
estrogen use

Ischemic Bowel Disease: CT Findings

luminal dilatation
bowel wall thickening
dilated mesenteric veins
edema in mesenteric fat
intramural gas
mesenteric or portal venous gas

Intestinal Obstruction - Etiology

adhesions (50%)
hernias (15%)
neoplasms (15%)
multiple causes (35.5%)

Small intestinal obstruction Mucha P Surg Clin NA 67;597-620, 1987

Colonic Hernias

external

protrusion of the bowel loop through a peritoneal defect to outside the abdominal cavity.

internal

protrusion of bowel into abdominal fossae, abnormal pouches, or peritoneal defects.

External Hernias - Types

inguinal
femoral
umbilical
obturator
incisional

Small Bowel Adenocarcinoma - Increased Incidence

familial polyposis
Gardner's syndrome
Peutz-Jeghers syndrome
Crohn's disease

Intestinal Ischemia: CT Diagnosis

Primary Findings

thrombosed mesenteric vessel (SMA/SMV)
intramural gas
portal venous gas
lack of bowel wall enhancement
ischemia of other organs

Intestinal Ischemia: Etiology

vascular occlusion
- emboli from heart common (lt. atrium or ventricle)
hx of cardiac disease including peripheral arterial insufficiency common

Intestinal Ischemia: Etiology

hypoperfusion without vascular occlusion
- cardiac failure (poor cardiac output)
sepsis
vascular insufficiency
trauma (shock bowel)

Intestinal Ischemia: CT Diagnosis

Secondary Findings

bowel dilatation
bowel wall thickening
bowel obstruction
mesenteric edema
mesenteric vascular engorgement
ascites

" Reformatting helical CT scans in multiple planes provides a new perspective for the evaluation of small bowel obstruction and may be useful in defining and characterizing obstruction."
CT of Small Bowel Obstruction: Another Perspective Using Multiplanar Reformations
Caoili EM et al.
AJR 2000;174:993-998

Normal Small Bowel Enhancement

Arterial Phase

Duodenum 120 +/- 5 HU
Jejunum 119 +/- 5 HU
Ileum 118 +/- 5HU

Portal Phase

Duodenum 111 +/- 4 HU
Jejunum 111 +/- 3 HU
Ileum 107 +/- 3HU

Septic Thrombophlebitis of the Mesenteric and Portal Vein

fact: infection is usually a result of a primary GI source

acute colonic diverticulitis (#1 cause)
appendicitis
inflammatory bowel disease
ileal diverticulitis
bowel perforation
pelvic infection
suppurative pancreatitis

Differential Diagnosis

lymphoma
carcinoid tumor
sarcoma
metastases to the bowel/mesentery
sclerosing mesenteritis
desmoid tumor

Sclerosing Mesenteritis is also known as;

retractile mesenteritis
nodular panniculitis
liposclerotic mesenteritis
xanthogranulomatous mesenteritis

Sclerosing Mesenteritis is also known as;

retractile mesenteritis
nodular panniculitis
liposclerotic mesenteritis
xanthogranulomatous mesenteritis

Calcification of a Mesenteric Mass: Differential Diagnosis

carcinoid tumor
treated lymphoma
old hematoma
sarcoma
sclerosing mesenteritis

Small Bowel Ischemia Due To Obstruction: CT Findings

reduced bowel wall enhancement
bowel wall thickening
mesenteric fluid
congestion of the small mesenteric walls
ascites

“ Helical CT is a highly sensitive method to diagnose or rule out intestinal ischemia in the context of acute small bowel obstruction.”
Helical CT Signs in the Diagnosis of Intestinal Ischemia in Small Bowel Obstruction
Zalcman M et al.
AJR 2000; 175:1601-1607

“ CT diagnosis was correct in 23 patients (96% sensitivity). There were 9 false positive diagnoses (93% specificity). The negative predictive value was 99%.”
Helical CT Signs in the Diagnosis of Intestinal Ischemia in Small Bowel Obstruction
Zalcman M et al.
AJR 2000; 175:1601-1607

Small Bowel Ischemia: CT Findings

SMA occlusion
SMV thrombosis
intramural and extraluminal air (pneumatosis intestinalis, pneumoperitoneum)
portal venous or mesenteric venous air
mesenteric edema and ascites
bowel wall thickening
abnormal bowel wall enhancement

Intestinal Ischemia: CT Diagnosis

Primary Findings

thrombosed mesenteric vessel (SMA/SMV)
intramural gas
portal venous gas
lack of bowel wall enhancement
ischemia of other organs

Intestinal Ischemia: Etiology

vascular occlusion
- emboli from heart common (lt. atrium or ventricle)
hx of cardiac disease including peripheral arterial insufficiency common

Intestinal Ischemia: Etiology

hypoperfusion without vascular occlusion
- cardiac failure (poor cardiac output)
sepsis
vascular insufficiency
trauma (shock bowel)

Intestinal Ischemia: CT Diagnosis

Secondary Findings

bowel dilatation
bowel wall thickening
bowel obstruction
mesenteric edema
mesenteric vascular engorgement
ascites

Septic Thrombophlebitis of the Mesenteric and Portal Vein

fact: infection is usually a result of a primary GI source

acute colonic diverticulitis (#1 cause)
appendicitis
inflammatory bowel disease
ileal diverticulitis
bowel perforation
pelvic infection
suppurative pancreatitis

Differential Diagnosis

lymphoma
carcinoid tumor
sarcoma
metastases to the bowel/mesentery
sclerosing mesenteritis
desmoid tumor

Sclerosing Mesenteritis is also known as;

retractile mesenteritis
nodular panniculitis
liposclerotic mesenteritis
xanthogranulomatous mesenteritis

Small Bowel Ischemia Due To Obstruction: CT Findings

reduced bowel wall enhancement
bowel wall thickening
mesenteric fluid
congestion of the small mesenteric walls
ascites

144 CT scans in 142 patients
73 cases w/ surgical correlation and 71 w/ clinical follow-up
ischemia diagnosed at surgery in 24 cases; of these CT made the correct diagnosis in 23 cases

Small Bowel Ischemia: CT Findings

SMA occlusion
SMV thrombosis
intramural and extraluminal air (pneumatosis intestinalis, pneumoperitoneum)
portal venous or mesenteric venous air
mesenteric edema and ascites
bowel wall thickening
abnormal bowel wall enhancement

Ischemic Bowel: Secondary CT Findings

Bowel obstruction
Infarction of other abdominal organs (spleen, liver, kidney)

Ischemic Bowel: Etiologies of Insufficient Blood Flow

Thromboembolism
Nonexclusive causes (slow flow)
Bowel obstruction
Neoplasms
Vasculitis
Inflammatory disease (i.e. appendicitis, diverticulitis)
Trauma
Chemotherapy or radiation therapy
corrosive injury

Ischemic Bowel: CT Findings

Bowel wall thickening (w/ or w/o the target sign)
Intramural pneumatosis
Mesenteric or portal venous gas
Mesenteric artery or vein thromboembolism
Mesenteric edema
Engorged mesenteric veins
Lack of bowel enhancement
Increased enhancement of thickened bowel