Incidence of Caesarean Scar Defect in Cases of Cesarean Section With and Without Bladder Flap Dissection

Anatomically Uterine niche is an iatrogenic pouch-like defect at the site of previous caesarean scar due to defective tissue healing. Radiologically niche should be defined as an indentation at the site of the CS scar with a depth of at least 2 mm. A niche can be subclassified in: (1) simple niche; (2) simple niche with one branch; (3) complex niche (with more than one branch). (1-3) Uterine niche occurs in up to 70% women with previous cesarean of whom 30% are symptomatic. Reported prevalence varies: 24-70% with transvaginal sonography (TVS) and 56-84% with gel/saline instillation sonohysterography (SHG).This may be an underestimation because many women are asymptomatic and also because clinicians may not recognize niche as a cause of symptoms due to unawareness. Prevalence of 45.6% was reported in a prospective observational study (n = 371) where sonohysterography was done six months post-cesarean. Prevalence increases with increasing number of previous cesareans. (1-5) Potential Risk Factors Niche forms due to poor healing of cesarean scar. Risk factors are: (5-8) 1. Factors Affecting Lower Uterine Segment: Cervical dilatation of \> 5 cm, \> 5 h duration of labour and advanced fetal station predispose to large niche due to thinner or less vascularized myometrium resulting in inadequate healing(5,6) 2. Level of Uterine Incision Lower uterine incision towards the cervix results in poor healing, as mucus secreted by cervical glands interferes with myometrial approximation. Mucus accumulation gradually increases the niche size also (5,7) Cesarean section done in advanced labour after cervical effacement and also creation of uterovesical fold of peritoneum influence the level of uterine incision. 3. Uterine Closure Techniques Single-layer, decidua sparing closure technique predisposes to incomplete closure, compared to single full-thickness closure. A strong myometrial scar with proper anatomical approximation without tissue strangulation minimizes risk of niches