One of the rare hernias occurring at the anterior abdominal wall is the Interparietal hernia which occurs at various anatomical (parietal) planes. An interparietal hernia has a hernial sac that passes between the layers of the anterior abdominal wall. This sac may be associated with, or communicate with, the sac of a concomitant ventral hernia. These types of hernias are difficult to suspect clinically or to diagnose radiologically hence it is usually missed or diagnosed lately or mostly as an intraoperative finding. In our case also, both USG could not diagnose it as an interparietal hernia, CT gave a picture of plane of the swelling, However, the extent of defect could not be accurately assessed which was finally seen intraoperatively and was treated accordingly by approximating transverse abdominis in upper 2/3^rd and lower 1/3^rd was sutured with internal oblique since the in lower part two leaf of transverse abdominis was far apart followed by double breasting of external oblique was done. This is a significant rare case interstitial type incisional hernia following post appendectomy as not many cases are found in the literature.

A 24-year-old male came to Surgical Op with complaints of swelling in the Right hypochondrium, which was gradually increasing in size for the past 6 months. It increased with straining and reduced on lying down. Patient underwent open emergency appendectomy one year back. At physical examination of patient, a 5 × 5 cm swelling with an expansile cough impulse was noted in the region of appendectomy scar. His laboratory investigation showed hemoglobin 17.1 g/dl, hematocrit-51.6%, leucocytes-12,900, platelets-249,000, Na-139 mg/dl, K-4.0 mg/ dl, Cl-106 meq/dl, CT abdomen-A defect seen in anterior abdominal wall along the right transverse abdominis muscle fibers of size 5 × 4.2 cm (AP × TR) through which herniation of omentum and ileal loops is noted with resultant laxity and stretching of the right external oblique muscle fibers noted (Figure 1 and Figure 2). The patient was posted for open repair with the diagnosis of Incisional interparietal hernia. Incision was made over the previous scar site and scar tissue was excised; Incision was deepened. Thick fibrous scar tissue was seen. External oblique fascial plane made. Defect of size 6 × 5 cm noted, hernial sac was adhered to external oblique muscle & aponeurosis. Sac opened and the contents were found to be small bowel and omentum (Figure 3). Adhesions between bowel and sac released and contents reduced. Defect was seen in transverse abdominis muscle with medial leaf 4 cm from incision site. After releasing bowel adhesions, to the inner surface of external oblique the Transverse abdominis muscle defect was approximated with 1.0 prolene only in upper 2/3^rd of defect

(Figure 4). In lower 1/3^rd Transverse abdominis muscle lateral leaf is seen near Anterior superior iliac spine and medial leaf seen near pubic symphysis hence medial leaf of muscle is sutured with internal oblique muscle (Figure 5). Double breasting of external oblique done (Figure 6). Suction drain placed skin sutured. Patient was comfortable post-operatively and was discharged on 4^th post-operative day. He was free of any symptoms after his follow at 3 months.

Bartolin was the pioneer to describe interparietal hernia in 1661 [1]. Interparietal hernia comprises nearly 0.01% - 1.6% of all hernias. Lower abdomen interparietal hernias are usually confused with the inguinal hernia mostly determined only at the time of operation. Sometimes lower abdomen intraparietal hernias frequently present with small bowel obstruction. Sub-types of Interparietal hernias include preperitoneal (between the peritoneum and transversalis fascia), Interstitial (between the muscle layers of external oblique and internal oblique), Superficial (between the skin and external oblique muscle) [2].

Prevalence of interstitial Sub-type is 60%. While other two combined accounts for 29%. Incidence of Interstitial hernia following abdominal surgeries is 10% [3].

These interparietal hernias predominantly occur in males and more common in children.

Interparietal hernia has a hernial sac which passes between layers of anterior abdominal wall. The sac may be associated with or communicating with sac of concomitant inguinal or femoral hernia. These types of hernia present with obstruction or strangulation, which is often missed or diagnosed late because swelling is often absent in preperitoneal variety.

Interparietal hernia can sometimes present as Intestinal Obstruction appearing as an odd inguinal hernia. So, it is essential for surgeons to have correct preoperative diagnosis and plan for emergency surgery [4]. After appendectomy incidence of hernia is usually due to infection of wound in advanced peritonitis associated with local purulent peritonitis. Other reasons are drain when fixed tightly through incision may cause fleshly internal oblique and transverse abdominis muscle leading to necrosis [5].

Repair of the incisional Intrabdominal hernia is mostly done by anatomical repair. When tissue is atrophic, a thin overlap kind of repair is done and sometimes sutured with underlying structure along with strengthening of above layer by double breasting techniques [6]. Sometimes these defects are best treated with a sheet of polypropylene mesh, with a margin measuring at least 6-8 cm beyond the periphery of the defect, placed between the peritoneum and transverses abdominis muscle. Both techniques can be successfully implemented if the correct indications based on the extent of the defect and the clinical characteristics of the patient are respected [7]. Interparietal hernias are a significant complication resulting after any abdominal surgical incision. Significantly large defects of this variety can be successfully managed entirely with laparoscopic technique using barbed suture for primary repair of defect with subsequent mesh reinforcement [8]. In our case patient underwent open primary defect closure with double breasting of the external oblique muscle.

The combination of Incisional in post appendicectomy scar site is a very rare event. Even though the clinical diagnosis is challenging the treatment is surgical repair. Mostly diagnosed intraoperatively and not many cases find mention in a review of the literature. Hence great caution needs to be excised in the management of the patient with such kind of presentation.

The authors declare no conflicts of interest regarding the publication of this paper.

Vishnukumar, K.G., Murthy, S.S., Rajasabapathy, A.K., Prabu, K.R.M. and Rekha, A. (2021) A Rare Interstitial Type of Post Appendectomy Incisional Hernia. Case Reports in Clinical Medicine, 10, 146-151. https://doi.org/10.4236/crcm.2021.105018