Abdominal Wall

I. ABDOMINAL REGIONS (Figure 6-1). The abdomen can be divided topographically into nine regions: right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right inguinal, hypogastric, and left inguinal.

II. CLINICAL PROCEDURE. In paracentesis (Figure 6-2), a needle is inserted through the layers of the abdominal wall to withdraw excess peritoneal fluid. (Knife wounds to the abdomen penetrate the layers of the abdominal wall in the same order.)

A. In the midline approach, the needle passes through the following structures: skin ► superficial fascia (Camper and Scarpa) linea alba transversalis fascia extraperitoneal fat parietal peritoneum.

B. In the flank approach, the needle passes through the following structures: skin superficial fascia (Camper and Scarpa) external oblique muscle ► internal oblique muscle transverse abdominis muscle —► transversalis fascia extraperitoneal fat parietal peritoneum.

III. INGUINAL REGION is a weak area in the anterior abdominal wall because it is where the testes and spermatic cord (in males) or the round ligament of the uterus (in females) penetrates during embryologic development.

A. The inguinal ligament is the coiled lower border of the external oblique muscle and extends from the anterior-superior iliac spine to the pubic tubercle.

B. The deep inguinal ring is an oval opening in the transversalis fascia located lateral to the inferior epigastric artery.

C. The superficial inguinal ring is a triangular defect of the external oblique muscle located lateral to the pubic tubercle.

D. The inguinal canal begins at the deep inguinal ring and ends at the superficial inguinal ring. It transmits the spermatic cord (in males) or the round ligament of the uterus (in females).

1. Types include direct inguinal hernia, indirect inguinal hernia, and femoral hernia.

2. Surgical repair a. In the Bassini repair, the transversalis fascia and conjoint tendon

(combined tendinous insertion of the transverse abdominis muscle and internal

Conjoint Tendon Bassini Repair

Figure 6-1. (A) A commonly used clinical method for subdividing the abdomen into specific regions using the subcostal plane (SCP), transtubercular plane (TTP; joining the tubercles of the iliac crests), and midclavicular lines (MC). EP = epigastric; HY- hypogastric; LH= left hypochondriac; LI = left inguinal; LL = left lumbar; RH = right hypochondriac; Rl = right inguinal; RL = right lumbar; UM = umbilical. (B) Surface projection of the stomach (S), pylorus (P), duodenum (D), liver (L), gallbladder (GB), ascending colon (AC), appendix (A), ileum (IL), descending colon (DC), sigmoid colon (SC), and rectum (R). (C) Surface projection of the duodenum (D), pancreas (P), kidneys (K), suprarenal gland (AD), and spleen (S). Many clinical vignette questions describe pain associated with a particular region of the abdomen. Knowing which viscera are associated with each region will help in answering the question (e.g., pain in the right lumbar region may be associated with appendicitis). (Adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed. Baltimore, Williams & Wilkins, 1992, pp 130, 131, 174.)

Figure 6-1. (A) A commonly used clinical method for subdividing the abdomen into specific regions using the subcostal plane (SCP), transtubercular plane (TTP; joining the tubercles of the iliac crests), and midclavicular lines (MC). EP = epigastric; HY- hypogastric; LH= left hypochondriac; LI = left inguinal; LL = left lumbar; RH = right hypochondriac; Rl = right inguinal; RL = right lumbar; UM = umbilical. (B) Surface projection of the stomach (S), pylorus (P), duodenum (D), liver (L), gallbladder (GB), ascending colon (AC), appendix (A), ileum (IL), descending colon (DC), sigmoid colon (SC), and rectum (R). (C) Surface projection of the duodenum (D), pancreas (P), kidneys (K), suprarenal gland (AD), and spleen (S). Many clinical vignette questions describe pain associated with a particular region of the abdomen. Knowing which viscera are associated with each region will help in answering the question (e.g., pain in the right lumbar region may be associated with appendicitis). (Adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed. Baltimore, Williams & Wilkins, 1992, pp 130, 131, 174.)

Linea alba

Paracentesis Abdominal

Extraperitoneal fat Transversalis fascia

Figure 6-2. A transverse section through the anterior abdominal wall shows the various layers that are penetrated by a needle during paracentesis, or by a knife wound. (Adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed, Baltimore, Williams & Wilkins, 1992, P 134.)

Linea alba

Extraperitoneal fat Transversalis fascia

Skin Superficial fascia External oblique muscle Internai oblique muscle Transversus abdominus muscle

Figure 6-2. A transverse section through the anterior abdominal wall shows the various layers that are penetrated by a needle during paracentesis, or by a knife wound. (Adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed, Baltimore, Williams & Wilkins, 1992, P 134.)

oblique muscle) are sutured to the shelving edge of the inguinal ligament (Poupart ligament).

b. In Cooper ligament repair (McVay method), the transversalis fascia and conjoint tendon are sutured to the periosteum of the pubic ramus (Cooper ligament, or pectineal ligament).

c. Surgical hernia repair may damage the iliohypogastric nerve, causing anesthesia of the ipsilateral abdominal wall and inguinal region, or the ilioinguinal nerve, causing anesthesia of the ipsilateral penis, scrotum, and medial thigh.

IV. SCROTUM (Figure 6-4) is an outpouching of the lower abdominal wall whereby layers of the abdominal wall continue into the scrotal area to cover the spermatic cord and testes.

A. Defects in development

1. Cryptorchidism occurs when the testis fails to descend into the scrotum. Normally, the testes descend at about 3 months of age. The undescended testis may be found within the inguinal canal or abdominal cavity. Bilateral cryptorchidism results in sterility.

2. Hydrocele occurs when a small patency of the processus vaginalis remains from embryologic development. The peritoneal fluid then can flow into the processus vaginalis, creating a fluid-filled cyst near the testes.

B. Cancer. Cancer of the scrotum metastasizes to the superficial inguinal nodes. Cancer of the testes metastasizes to the deep lumbar nodes near the renal hilus because the testes develop embryologically within the abdominal cavity and then descend into the scrotum.

C. Trauma. Extravasated urine from a saddle injury will leak into the superficial perineal space located between Colles fascia and the dartos muscle (layer 2) and the external spermatic fascia (layer 3) |see Figure 6-4].

D. In a vasectomy, the scalpel cuts through the following structures: skin —► Colles fascia and dartos muscle external spermatic fascia —► cremasteric fascia and muscle ► internal spermatic fascia —► extraperitoneal fat. The tunica vaginalis is not cut.

Extravasated UrineLayers Abdominal Fascia

Type of

Hernia Characteristics

Direct Protrudes directly through the anterior abdominal wall within the Hesselbach triangle*

inguinal Protrudes medial to the inferior epigastric artery and vein* Common in older males; rare in women

Clinical signs include: a mass in the inguinal region that protrudes on straining and disappears at rest (i.e., it is easily reduced), constipation, and prostate enlargement; hernia can be detected with the pulp of the finger

Indirect Protrudes through the deep inguinal ring to enter the inguinal canal; may exit through inguinal the superficial inguinal ring into the scrotum

Protrudes lateral to the inferior epigastric artery and vein* Protrudes above and medial to the pubic tubercle* Common in young males More common than direct inguinal hernia

Clinical signs include: a tender, painful mass in the inguinal region that continues into the scrotum; hernia can be felt with the tip of the finger

Femoral Protrudes through the femoral canal below the inguinal ligament Protrudes below and lateral to the pubic tubercle* Protrudes medial to the femoral vein More common in females; appears on the right side Prone to early strangulation

'The Hesselbach (inguinal) triangle is bounded laterally by the inferior epigastric artery and vein, medially by the rectus abdominis muscle, and interiorly by the inguinal ligament. tDistinguishing feature of direct versus indirect hernia. ^Distinguishing feature of indirect versus femoral hernia.

Figure 6-3. (A) Anatomy associated with direct and indirect inguinal hernias. (B) Anatomy associated with a femoral hernia, dr = deep inguinal ring; IE = inferior epigastric artery and vein; FA = femoral artery; FN = femoral nerve; FV= femoral vein; IL = inguinal ligament; LL = lacunar ligament; PL = pectineal (Cooper) ligament; PT- pubic tubercle; RA = rectus abdominis muscle; sr= superficial inguinal ring.

Pubic Tubercle
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