The minor calices receive urine from the papillary ducts and represent the proximal parts of the tube that will eventually form the ureter (Fig. 4.153). In the renal sinus, several minor calices unite to form a major calyx, and two or three major calices unite to form the renal pelvis, which is the funnel-shaped superior end of the ureters.
A single large renal artery, a lateral branch of the abdominal aorta, supplies each kidney. These vessels usually arise just inferior to the origin of the superior mesenteric artery between vertebrae LI and LII (Fig. 4.154). The left renal artery usually arises a little higher than the right, and the right renal artery is longer and passes posterior to the inferior vena cava.
As each renal artery approaches the renal hilum, it divides into anterior and posterior branches, which supply the renal parenchyma. Accessory renal arteries are common. They originate from the lateral aspect of the abdominal aorta, either above or below the primary renal arteries, enter the hilum with the primary arteries or pass directly into the kidney at some other level, and are commonly called extrahilar arteries.
Multiple renal veins contribute to the formation of the left and right renal veins, both of which are anterior to the renal arteries (Fig. 4.154A). Importantly, the longer left renal vein crosses the midline anterior to the abdominal aorta and posterior to the superior mesenteric artery and can be compressed by an aneurysm in either of these two vessels (Fig. 4.154B).
The lymphatic drainage of each kidney is to the lateral aortic (lumbar) nodes around the origin of the renal artery.
The ureters are muscular tubes that transport urine from the kidneys to the bladder. They are continuous superiorly with the renal pelvis, which is a funnel-shaped structure in the renal sinus. The renal pelvis is formed from a condensation of two or three major calices, which in turn are formed by the condensation of several minor calices (see Fig. 4.153). The minor calices surround a renal papilla.
The renal pelvis narrows as it passes inferiorly through the hilum of the kidney and becomes continuous with the ureter at the ureteropelvic junction (Fig. 4.155). Inferior to this junction, the ureters descend retroperitoneally on the medial aspect of the psoas major muscle. At the pelvic brim, the ureters cross either the end of the common iliac artery or the beginning of the external iliac artery, enter the pelvic cavity, and continue their journey to the bladder.
At three points along their course the ureters are constricted (Fig. 4.155):
The first point is at the ureteropelvic junction.
The second point is where the ureters cross the common iliac vessels at the pelvic brim.
The third point is where the ureters enter the wall of the bladder.
Kidney stones can become lodged at these constrictions.
The ureters receive arterial branches from adjacent vessels as they pass toward the bladder (Fig. 4.155):
The renal arteries supply the upper end.
The middle part may receive branches from the abdominal aorta, the testicular or ovarian arteries, and the common iliac arteries.
In the pelvic cavity, the ureters are supplied by one or more arteries from branches of the internal iliac arteries.
In all cases, arteries reaching the ureters divide into ascending and descending branches, which form longitudinal anastomoses.