18 Abdominal Wall
18.1 Penile Root Block
In a penile root block, the two dorsal nerves of penis are blocked. The dorsal nerves of the penis are terminal branches of the pudendal nerve (S2–S4), which run through the subpubic space caudal to the symphysis slightly paramedian up to the dorsal side of the penis. This subpubic space is bordered cranially by the symphysis, caudally by the corpora cavernosa penis, and anteriorly by the fascia of Scarpa (inner membranous layer of the superficial abdominal fascia; Fig. 18.1). The nerves are located lateral to the dorsal arteries of penis and the unpaired deep dorsal vein of penis. This neurovascular bundle runs between the fascia of Buck (deep fascia of penis) and the tunica albuginea (Fig. 18.2). Cranially, there is a connection between the fascia of Buck and the fascia of Scarpa.
The dorsal penile nerves supply sensory innervation to the glans penis and the distal two thirds of the penile skin. The proximal third of the penile skin receives its sensory supply from the genitofemoral nerves and iliohypogastric nerves.
18.1.2 Technique of Penile Root Block
Symphysis, penile root.
The child is in the supine position.
The skin caudal to the symphysis is disinfected, then the symphysis is palpated and the penis is pulled slightly caudally or alternatively fixed caudally with an adhesive bandage across the thigh. An incision is made with a short-bevel needle (25 or 27 G) paramedian (0.5–1 cm lateral to the midline) just caudal to the symphysis (Dalens et al 1989). The needle is advanced in a slight mediocaudal direction (Fig. 18.3) into the subpubic space until the fascia of Scarpa is perforated (clear “fascia click”). After negative aspiration, the local anesthetic is injected. Then a further injection is made on the opposite side using the same technique.
Local Anesthetic, Dosage
Bupivacaine 0.5% (5 mg/mL), 1 mL/kg body weight per side (total volume 0.2 mL/kg body weight).
No epinephrine is added to the local anesthetic since the arterial blood supply of the penis is an end-arterial blood supply.
18.1.3 Indications and Contraindications
Pain after circumcision and interventions in the area of the front half of the penis (e.g., uncomplicated hypospadias repair).
General contraindications (Chapter 20.2).
18.1.4 Complications, Side Effects, Method-Specific Problems
If the injection direction is too medial and too caudal, a hematoma may form due to perforating the fascia of Buck and injuring the dorsal vessel. Necrosis of the glans penis may develop from compression of the hematoma on the vessels (Sara and Lowry 1985). The risk of a hematoma is increased in a median puncture (Dalens et al 1989).
If the injection direction is too caudal, accidental perforation of the tunica albuginea may occur with puncture of the corpora cavernosa und injection of the local anesthetic into the corpora cavernosa. The result is similar to an intravascular local anesthetic injection.
Puncture of the urethra if the injection direction is too median and too caudal (Soh et al 2003).
Osteomyelitis of the ischium (Abaci et al 2006).
Analgesia gaps may occur in the area of the frenulum. The meatus is not anesthetized in the penile root block.
18.1.5 Remarks on the Technique
Burke et al (2000) report on temporary ischemia of the glans penis after using ropivacaine 0.75% (7.5 mg/mL). Due to the vasoconstrictive properties of ropivacaine, the scientific working group for pediatric anesthesia of the German Society of Anesthesia and Intensive Medicine (DGAI) has currently reached no conclusive assessment of the use of ropivacaine in end-arterial areas (Mader et al 2007).
As an alternative to the technique described above, the block can also be made by a single median puncture (Bacon 1977). After bone contact with the symphysis, the needle is withdrawn slightly and advanced directly caudal to the symphysis. After aspiration, the local anesthetic is applied. This technique increases the risk of a hematoma (see above).
18.2 Ilioinguinal Nerve Block
The iliohypogastric nerve (T12, L1) and ilioinguinal nerve (L1) descend from the lateral border of the psoas major muscle between the renal capsule and the quadratus lumborum muscle. Both nerves run parallel and cranial to the iliac crest between the internal oblique muscle and the transversus abdominis muscle (Fig. 18.4) and supply sensory innervation to the skin of the lateral hip region, the mons pubis, and the anterior upper part of the scrotum or the labia majora.
A linear transducer is placed on the lateral abdominal wall medial or slightly craniomedial to the anterior superior iliac spine and the iliohypogastric and the ilioinguinal nerves are visualized in the short axis (Fig. 18.5). The nerves can be visualized within a “lenticular” double fascia between the internal oblique muscle and the transversus abdominis muscle as hypoechoic structures surrounded by the hyperechoic fascia (Fig. 18.6).
18.2.3 Technique of Ilioinguinal Nerve Block
Anterior superior iliac spine, muscles of the abdominal wall in the ultrasound image (see TAP block; Chapter 13.3), double fascia between the transversus abdominis muscle and the internal oblique muscle.