Findings : Colo-colic intussusception in descending colon likely due to Lipoma.

Intussusception :

When one segment of the bowel is pulled into itself or a neighbouring loop of the bowel by peristalsis. 

The prolapsing part of the bowel is described as the Intussusceptum, while the distal segment of bowel receiving the intussusceptum is described as the intussuscipiens.

An asymptomatic transient intussusception without an attributable cause is an incidental finding in abdominal imaging and can be considered physiological both in children and adults.

The classic triad of intermittent abdominal pain, vomiting, and right upper quadrant mass, plus occult or gross blood on rectal examination.

Classic physical exam findings include an oblong palpable mass in the right upper quadrant described as “sausage-like” with a paucity of palpable bowel in the right lower quadrant. Sometimes the parents will report the passing of red stool (“currant jelly” stool) which is stool mixed with blood and mucus and is a sign that bowel ischaemia has occurred.

Intussusception can occur essentially anywhere. Depends on location it classified as :

• ileocolic: most common (75-95
• ileoileocolic: second most common
• ileoileal and colocolic: uncommon
• gastric intussusception: rare

Dignostic features on Ultrasoundincludes :

·         target sign (also known as the doughnut sign)

·         pseudokidney sign

·         crescent in a doughnut sign

·         absent blood flow in the intussusceptum (a contraindication to enema reduction)

·         free fluid within the intusussceptum

·         a lead point within the intussusceptum mass eg a lymph node

Features that favour ileocolic over small bowel intussusception 

·         presence of a hyperechoic core, representing mesenteric fat

·         diameter of the fatty core exceeding that of the outer wall

·         larger anteroposterior diameter (mean 2.6 cm vs. 1.4 cm)

o    diameter over 2 cm strongly argues in favour of ileocolic

·         thicker outer hypoechoic wall (mean 0.6 cm vs 0.4 cm)

·         lymph nodes inside the intussusception

·         greater length of intussusceptum (>3 cm strongly favouring ileocolic)

o    average length of ileocolic 53.4 mm, compared with small bowel intussuception, with an average length of 27.6 mm 

·         absence of a normal sonographic appearance to the ileocaecal junction and ascending colon

Small bowel intussusception has a predilection for the paraumbilical to left upper/lower quadrants of the abdomen. While typically transient, surgical management may be required if spontaneous reduction is unlikely to occur.

Sonographic features which are considered more consistent with an uncomplicated clinical course include:

·         outer diameter <2.5 cm 

·         preserved bowel wall motility

·         no identifiable lead point

·         invagination length <3 cm

Differential diagnosis :

The main differential is that of transient intussusception, which is an incidental finding requiring no treatment or follow-up.

Other differentialsincludes :

·         primary bowel tumour

·         metastases and lymphoma

·         intestinal lipoma (without intussusception)

·         Meckel diverticulum

·         gallstone ileus