Lymphatic malformation (LM) is one of the slow-flow vascular anomalies caused by abnormal embryologic development of the lymphatic system. LM manifests before the age of 2 years in >90% of patients, and has been called ‘lymphangioma’ or ‘cystic hydroma’ in the past (1-3). It most commonly occurs in the neck, followed by the trunk and extremities. However, intra-abdominal LM is rare, only accounting for 5-10% of cases (4-6). Abdominal pain and other gastrointestinal symptoms such as abdominal distension, vomiting and constipation are present in children with abdominal LM (4,6,7), which is different from the painless LM mass typical in the more common sites (2,8). LMs are classified by size as macrocystic, microcystic or mixed patterns, which is of therapeutic importance (2). In the abdomen, the majority of LM are classified as a macrocystic lesion (6-8), arising from mesentery, retroperitoneum or solid organs (4,8,9).

Historically, surgical resection has been the standard treatment regardless of location (1,2,7). Percutaneous sclerotherapy as a minimally invasive method by image-guidance has been preferred treatment applied for LM with good outcomes over the past years (1,2,6-8). However, surgical resection for intra-abdominal LM, especially with laparoscopy, has some advantages. In The Second Affiliated Hospital Of Xi'an Jiaotong University (Xi'an, China), laparoscopic surgery has been widely used in the pediatric population, and so the present retrospective analysis of intra-abdominal LM treated with laparoscopy was undertaken to provide pediatric surgeons with more experience in diagnosis and treatment of this lesion.

Intra-abdominal LM is rare in children and challenging for surgeons to differentiate from other cystic lesions (8). Surgical excision is indicated for patients with LM who have complications such as infection or hemorrhage (2). Laparoscopic surgery is a minimally invasive method for treating intra-abdominal LM, and the rapid development of laparoscopic technique has benefitted patients with LM (11). Because of less intraoperative blood loss, postoperative pain and scarring, laparoscopic surgery has more advantages compared with conventional open surgery (11).

The majority of LMs are noted in the first few years of life, and grow proportionately with the growth of children (2). Intra-abdominal LMs are usually diagnosed with acute gastrointestinal symptoms because of complications of large LMs at the mean age of 5 years (4), which is similar to the results of the present study. Female patients outnumbered male in some previous studies (4,6); male predominance was reported in other studies (7,12,13), but there was no sex predilection in the present cases, which may be because of the small number of patients included.

The majority of patients of intra-abdominal LM are reported to have acute gastrointestinal symptoms (4,6,13), which differed from the majority of LMs presenting as a painless mass (1,2,8) diagnosed clinically and radiologically (7,14). Although varied symptoms were present in 80-96% of patients, abdominal pain was the most common symptom of intra-abdominal LMs (4,6,7,12) as in the present study. Macrocystic LMs were the most common pattern of intra-abdominal LMs although combined and microcystic were also identified in the abdomen (4,6,7,9,13). Except for symptoms from mass effect and volvulus, complications including intracystic hemorrhage and infection occurred in 60% of the present patients and may be the main cause of acute abdomen (3). Therefore, the diagnosis was challenging preoperatively and misdiagnosis occurred in ~1/3 of patients with intra-abdominal LM (4).

On imaging, cystic lesions such as teratoma, enteric duplication cyst and ovarian cyst can be confused with intra-abdominal LMs (8). To avoid radiation, ultrasound is the first choice to evaluate intra-abdominal LMs in children, which typically shows multilocular cystic masses. Further evaluation with cross-sectional imaging provides additional information on diagnosis and location of the lesion. However, although imaging findings play an important role in the diagnosis of intra-abdominal LMs, there is no highly specific radiological presentation that makes the definitive diagnosis (4,8).

Percutaneous sclerotherapy by image-guidance has been preferred as primary treatment modality for LM over the past years (1,2,15). However, repeated sclerotherapy with residual lesions (6,7,13) cannot replace surgery as the first treatment modality because of frequent recurrence (3,16-18). The final diagnosis was usually corrected by intraoperative findings and the histopathology of lesions (8,19), which makes resection important (4,11,12,16,17,20). Surgical resection is a potential curative procedure for LM (19), and the laparoscopic approach can be performed to find the location and dissect primarily without large scars (4,11).

In fact, it is also challenging to remove intra-abdominal LMs completely because of the involvement of neighboring structures such as blood vessels and the alimentary tract (4,17), and recurrence may result after incomplete resection (3). Therefore, segmental resection of the intestine is usually necessary to achieve complete the resection of and decrease the potential recurrence of LMs (3,4,20). A total of five patients in the present study underwent intestinal anastomosis after segmental intestinal resection, which was common (84% of patients) in a previous study (4) and in case reports (11,16-18). In some circumstances, LM cannot be resected completely because of the involvement of vital structures, and percutaneous sclerotherapy may be suitable for recurrence after surgical resection (6).

Ileus and recurrence are the frequent postoperative complications of surgical resection (3,4). With the exception of residual lesion in one patient who underwent incomplete resection, there were no instances of recurrence or ileus in our patients during the mean follow-up period of 35 months. Conversion to laparotomy occurred in patients from the current study who had large retroperitoneal LM, suggesting that these larger-volume lesions had more involvement of adjacent organs and tissues (9). It is worthwhile to perform laparoscopic exploration to confirm the origin and extent of the lesion as well as the possibility of laparoscopic resection. Furthermore, the classification of mesenteric LM by radiological information would give surgeons guidance in preoperative planning (4).

Compared with adults, pediatric laparoscopic surgery of intra-abdominal LM is challenging because of the smaller space in children. Puncturation and aspiration guided by laparoscopy is recommended to minimize the lesion and to provide more space for laparoscopic resection because of benign cysts (3). After the removal of lesions, segmental intestinal resection and anastomosis of can be finished by expanding the umbilical trocar incision in some cases. Complete resection can be performed by laparoscopy without relapse during the follow-up. This approach was proved to be effective for treating intra-abdominal LM in the present study.

To the best of our knowledge, this is the largest study of laparoscopic resection of intra-abdominal LM in the pediatric population. However, there were limitations to the current study, as in the majority of case series: Small number of patients, retrospective review and no controls because of the rarity of intra-abdominal LMs.

In summary, intra-abdominal LM in pediatric population of the present study was diagnosed by initial acute gastrointestinal symptoms, mainly onset of abdominal pain at the mean age of 5 years. Macrocytic LM was the most frequent type of intra-abdominal LM and was effectively resected laparoscopically. Complete resection was associated with a lower recurrence, which was usually accompanied by segmental intestinal resection.