Mesenteric cysts are rare benign lesions occurring in the abdomen. The cystic lesions can be asymptomatic or present with a specific symptoms. When discovered, treatment is either open or laparoscopic surgery. We present a case of 9 years old boy with the complain of abdominal pain and urinary incontinence. On examination abdomen was soft and distended, No lump felt. Ultrasound scan of the abdomen done on 3.10.21 suggest the large Anechoic cyst in abdomen as detailed likely S/o retroperitoneal lymphangioma, mildly thickened bladder wall again on 27 October 21 USG of the abdomen repeated impression was there is evidence of large cystic thin walled lesion in the midline and to the right side of abdomen measuring approx. 11.0x 4.0x9.2 cm in size. The cyst is traversing along the mesenteric vessels and is seen extending up to the retroperitoneal region. Posteriorly the cyst is seen abutting the great vessels. Internal echoes are seen within the cyst with few partial thick septa likely lymphatic malformation. CECT was performed on 4 October 2021 A well-defined unilocular cystic lesion with thin imperceptible walls is seen in the mesentery in right lumbar region. It measures 10x 7.3 x6.5 cm. no evidence of sepatations/ enhancing solid component/ calcification seen. Anteriorly lesion is abutting and causing displacement of small bowel loops. Posterolaterally lesion is abutting and displacing the ascending colon. Poseromedially it is abutting the psoas muscles, Infra renal IVC and aorta. Laterally it was reaching up to the abdominal wall. Medially lesion is crossing the mid line and reaching upto left lateral border of infra renal aorta. Medially it is insuinating between the superior mesenteric vessels and IVC & aorta superiorly it is abutting the segment VI of liver and D3 segment of duodenum. Mesenteric vessels are seen along the wall of the lesion. Findings were suggestive of large thin walled unilocular cystic lesion in mesentery in right lumbar region as described possibility of lymphangioma and mesenteric lymphadenopathy. Exploratory laparotomy was done. The excised cyst revealed the 15x 10 cm thin walled with fibrinous exudates and containing light brown fluid. The patient had uneventful postoperative recovery. Histopathology of the cyst showed cyst wall made up of loose fibro collagenous tissue with multiple foci of lymphoid infiltrate and vascular proliferation. Focally cuboidal cells are seen lining the wall.

Mesenteric cysts are rare benign lesions occurring in the abdomen. The cystic lesions can be asymptomatic or present with a specific symptoms.