MRI of the penis

Abstract

MRI of the penis is an expensive test that is not always superior to clinical examination or ultrasound. However, it shows many of the important structures, and in particular the combination of tumescence from intracavernosal alprostadil, and high-resolution T(2) sequences show the glans, corpora and the tunica albuginea well. In this paper we summarise the radiological anatomy and discuss the indications for MRI. For penile cancer, it may be useful in cases where the local stage is not apparent clinically. In priapism, it is an emerging technique for assessing corporal viability, and in fracture it can in most cases make the diagnosis and locate the injury. In some cases of penile fibrosis and Peyronie's disease, it may aid surgical planning, and in complex pelvic fracture may replace or augment conventional urethrography. It is an excellent investigation for the malfunctioning penile prosthesis.

Figure 1

Cross-sectional penile anatomy.

Figure 2

T₂ (a) and T₁ (b) weighted sequences through the tumescent penis. Black arrowheads mark the tunica albuginea, and white arrowheads Buck's fascia. In (a) the thick white arrow shows the superficial dorsal vein and the thinner white arrows the deep dorsal vessels. The cavernosal arteries are marked by black arrows. The urethra, lying in the middle of the corpus spongiosum, is marked by an asterisk.

Figure 3

T₂ weighted sagittal section close to the midline (a) after intracavernosal alprostadil and (b) without tumescence. Black arrows mark the tunica albuginea, large white arrows the corpus spongiosum, small white arrows the urethra within it, and small black arrows the bulbocavernosus muscle. The white arrow head indicates the entry of the urethra into the roof of the bulb, and an asterisk marks the glans. In (a) the “corrugated” appearance of the corpus cavernosum is because of the midline septum, and normal. Note the considerably thicker tunica albuginea in the detumescent state, and the lower signal in corpus cavernosum; the glans is not in the midline sagittal plane.

Figure 4

Ulcerating lesion on the glans (white arrowheads, with a white arrow showing the ulcerated part), pT2 on histology and correctly called T2 on MRI. CC, corpus cavernosum; S, the spongiosal part of the glans.

Figure 5

T₁ weighted scan 10 min after caverject in low-flow priapism after a right-sided Winter shunt. The left corpus cavernosum (L) is infarcted, and a little expanded, but the right (R) enhances normally. This is an unusual pattern but can be produced by surgical intervention.

Figure 6

Axial T₂ (a) and early dynamic post-contrast gradient echo images (b) in high-flow priapism. The fistula (confirmed on ultrasound and angiography) is shown by the arrowheads in each. It is seen as an area of heterogeneous signal (with elements of flow void) on T₂, and is associated with earlier enhancement in the right corpus cavernosum (R) than the left (L).

Figure 7

Transverse T₂ weighted image in a patient with surgically confirmed penile fracture. The white arrowheads show the tunica albuginea, and the white open arrowheads a little of Buck's fascia. A urinoma (F) lies below the Dartos fascia (black open arrowheads). The fracture is seen as a defect in the ventral aspect of both corpora cavernosa (black arrowheads), with, in addition, disruption of the normally high-signal corpus spongiosum (black asterisk).

Figure 8

Peyronie's disease. T₂ coronal image showing tunical plaque in the distal right corpus cavernosum (white arrowheads), with moderate distal waisting. Intracavernosal fibrosis is seen on the left (white arrows).

Figure 9

Aneurysmal dilation of the penile prosthesis (white arrow), causing a palpable lump and poor inflation. Note the tubing extending to the pump in the scrotum (white arrowheads). No fluid is seen around it to indicate infection.