There are no three physiological narrowings in the upper urinary tract: a new concept of the retroperitoneal anatomy around the ureter

Abstract

The widely held dogma of three physiological narrowings in the upper urinary tract has proven incorrect by recent several studies using computed tomography images. There are only two common obstruction sites: the upper ureter and the ureterovesical junction. The second narrowing, where the ureter crosses the iliac vessels, cannot be regarded anymore as a common obstruction site. The mechanism by which stones lodge in the upper ureter is explained anatomically by the change in ureteral mobility and compliance at the level where the ureter exits the perirenal space. This level can be identified radiologically as the point where the ureter crosses under the ipsilateral gonadal veins, termed the "crossing point". Kinking of the upper ureter is another manifestation of this anatomical phenomenon, visible in radiological images. It is caused by loosening of the ureter at or above the crossing point (within the perirenal space), corresponding with renal descent such as during the inspiratory phase. This new anatomical discovery in the retroperitoneum will not only bring about a paradigm shift in terms of the physiological narrowings in the upper urinary tract, but may also lead to the development of new surgical concepts and approaches in the area.

Keywords: Anatomy; Computed tomography; Crossing point; Retroperitoneal space; Ureter; Urinary stone.

Fig. 1

The first publicized description of three physiological narrowings in the upper urinary tract, in 1954 (Dodson AI. Anatomy and surgical approach to the urogenital tract in the male. In: Campbell M, ed. Urology. Philadelphia and London: WB Saunders Company; 1954:11–17) [6]. No reference was provided for this description

Fig. 2

Distributions of upper urinary stone location assessed by computed tomography. Recent several studies have revealed that stones do not commonly lodge at the level where the ureter crosses the iliac vessels. The two peak sites where stones lodge in the upper urinary tract are the upper ureter and the ureterovesical junction (UVJ). UPJ Ureteropelvic junction. (The data presented in the figure are from Eisner et al. [7], Song et al. [8], and Moon et al. [9])

Fig. 3

Photographs of the retroperitoneal region of a cadaveric specimen. a Macroscopic view. The retroperitoneum of the cadaver is fixed in formalin, and the intraperitoneal organs are removed. b Magnified view around the upper ureter. The ureter can be observed beneath the layer of gonadal vessels. The ureter is first located in the perirenal portion; thereafter, it is fixed firmly to the anteromedial aspect of the psoas major muscle. The level where the ureter exits the perirenal space approximately corresponds to the level where the ureter crosses under the ipsilateral gonadal vein. This point is termed the “crossing point.” (Cited and revised from [12])

Fig. 4

Box plot of the distance between the crossing point and stone location (as discovered in [13]). The peak site of urinary stone distribution in the upper ureter is corresponding approximately to the level of the crossing point on both sides. Kn Kidney, GV Gonadal vein, Ur Ureter

Fig. 5

Distribution of stones, by size, relative to the crossing point (cited from [13]). No large stones are observed below the level of the crossing point. Kn Kidney, GV Gonadal vein, Ur Ureter

Fig. 6

Oblique coronal computed tomography images of stones lodging at the level of the crossing point. a A 27-year-old male with a urinary stone at the level of the crossing point, b A 53-year-old male with a urinary stone at the level of the crossing point. When a stone lodges in the urinary tract (white arrows), the upstream tract dilates because of urinary stasis. Thereby, the crossing point mimics the ureteropelvic junction, the location where the diameter of the urinary tract originally changes

Fig. 7

Kinking of the upper ureter in a reconstructed excretory coronal CT image of a 63-year-old male (cited from [12]). In retrograde pyelography or computed tomography (CT) urography, kinking of the upper ureter is not rare, although usually ignored

Fig. 8

Underlying mechanism of kinking of the upper ureter (cited from [12]). The ureter is relatively mobile in the perirenal space (above the level of the crossing point), allowing it to loosen when the kidney descends. This phenomenon manifests as kinking of the ureter. Kn Kidney, IVC Inferior vena cava, Ao Aorta, GV Gonadal vein, GA Gonadal artery, Ur Ureter, PM Psoas muscle

Fig. 9

Fluoroscopic images of the dynamic movement of the upper ureter corresponding to that of the kidney. Angiography of a 73-year-old female with vaginal bleeding due to metastasis of ovarian cancer. Dynamic movement of the ureter correlating with that of the kidney is well visualized in fluoroscopy. Kinking arises when the kidney descends during the inspiratory phase, resulting from loosening of the upper ureter