Chapter 29: The kidneys, ureters and suprarenal glands
The kidneys (L., ren; Gk, nephros; hence the adjectives renal and nephric) belong to the urinary system, maintain the ionic balance of the blood, and excrete waste products as urine. They are reddish-brown organs covered by a thin, glistening, fibromuscular capsule that normally can be stripped off easily. Each kidney has anterior and posterior surfaces, upper and lower poles, and lateral and medial borders. The medial border is indented at the hilus, where blood vessels enter and leave, and there the ureter emerges. Each kidney is composed of a paler cortex and a darker medulla (fig. 29-1). The kidneys lie obliquely along the vertebral column, abutting the psoas major muscles.
Relations (fig. 29-2).
The upper pole of the kidney is covered by the suprarenal gland. Anteriorly, the right kidney is related to the liver, duodenum, ascending colon or right colic flexure, and small intestine. The left is related to the spleen, stomach, pancreas, descending colon or left colic flexure, and small intestine. Posteriorly, the kidneys are related to rib 12 and the diaphragm, psoas major, quadratus lumborum, and transversus abdominis (see fig. 29-5).
The upper part of the kidney is usually separated by the diaphragm from the pleura and lung. In the vertebrocostal trigone, however, the kidney and pleura may be separated only by connective tissue (see fig. 25-13B).
The kidneys are retroperitoneal. Certain areas of each kidney are covered in anteriorly by peritoneum, whereas others are "bare" (fig. 29-2).
In the erect position, the kidneys are opposite the first four lumbar vertebrae; they are one vertebral level higher when the subject is recumbent. The right kidney is frequently a little lower than the left (probably because of the liver), and its lower pole may be palpable. The levels alter with respiration as well as with posture.
The hilus for the renal vessels and ureter is situated on the medial border and leads into a recess termed the renal sinus. The sinus contains the renal vessels and an expansion of the ureter termed the pelvis. Within the sinus, the ureteric pelvis usually divides into two or three short tubes, the major calices, each of which subdivides into 7 to 14 minor calices (fig. 29-3). Each minor calyx receives the openings of collecting tubules on papillae that project into the calices (see fig. 29-1).
The ureter and renal vessels near the hilus form the pedicle, important variations of which are common. The renal vein (figs. 29-2 and 29-4) is anterior, the ureter is posterior, and the arteries more or less between.
Renal Fascia (fig. 29-5).
The kidney is enclosed in a condensation of the extraperitoneal tissue termed the renal fascia. Its anterior layer continues across the median plane, whereas the posterior layer merges with the prevertebral connective tissue. The two layers are fused strongly superior to, and weakly inferior to the suprarenal gland. Perirenal (or perinephric) fat lies between the fascia and the renal capsule. Pararenal fat is situated external to the renal fascia.
The renal arteries arise from the aorta, and the right one passes posterior to the inferior vena cava (see figs. 29-2 and 29-4). Renal segments based on the arterial distribution have been identified (fig. 29-6). The left renal vein, which is longer than the right, passes anteiro to the aorta and drains not only the kidney but also the suprarenal gland, gonad, diaphragm, and body wall (see fig. 29-4). Lymphatic drainage is into adjacent nodes and thence into lumbar nodes.
Extensions of the celiac (aorticorenal) and intermesenteric plexuses accompany the renal arteries, and the splanchnic nerves supply branches that include pain fibers from the ureteric pelvis (see figs. 30-4 and 32-6).
Congenital anomalies of the kidneys include lobation (which is normally evident at birth), so-called accessory (e.g., polar) arteries, duplications (e.g., of ureters), ectopia and malrotation (e.g., pelvic kidney and horseshoe kidney), and cystic disease.
The ureter is a retroperitoneal, distensible muscular tube that connects the kidney with the bladder. In position, the upper half is abdominal, the lower half pelvic. The ureter commences as a dilatation, the pelvis, posterior to the renal vessels, and it descends on the psoas major. It crosses anterior to the bifrucation of the common iliac artery, courses along the lateral wall of the pelvis, and turns medially to reach the bladder. Near the ischial spine, the ureter turns downward, anteriorward, and medially just inferior to the uterine vessels, about 2 cm from the cervix (where it may be endangered in hysterectomy).
The ureter may be constricted (1) at the narrowing of the ureteric pelvis, (2) where it crosses the pelvic inlet, and (3) during its course through the wall of the bladder. These are potential sites of obstruction or for kidney stones to lodge.
The ureter is supplied by nearby arteries (renal, gonadal, and vesical) and from adjacent nervous plexuses (renal and hypogastric). Obstruction by a renal calculus (stone) causes acute distension and severe pain (renal colic). Depending on the level of obstruction, the pain of renal (actually ureteric) colic may be referred to the lumbar or the hypogastric region or to the external genitalia.
The suprarenal glands are paired endocrine organs situated superior to the kidneys (hence suprarenal; c.f. epinephrine).
Each suprarenal gland consists of two distinct endocrine organs, the cortex and the medulla. Some of their hormones are essential to life. Each suprarenal gland is surrounded by renal fascia and lies on the superomedial aspect of the front of the kidney (see fig. 29-2). The right gland is in contact with the bare area of the liver and projects posterior to the inferior vena cava (see fig. 30-3). The left gland, a little different in shape, is related in front to the lesser sac, the splenic artery, and the pancreas (see fig. 26-6). Both glands lie against the diaphragm.
Accessory cortical tissue may sometimes be found near the kidney or in the pelvis. The suprarenal medulla is part of the chromaffin system, other portions of which are found near sympathetic ganglia along the abdominal aorta and are termed paraganglia or para-aortic bodies.
Blood Supply (see fig. 29-4).
The suprarenal glands are supplied by multiple and variable arteries (from the inferior phrenic and renal arteries and the aorta). The suprarenal vein emerges from a hilus and enters the inferior vena cava (right side) or the renal vein (left side).
The celiac plexus and splanchnic nerves supply branches. Most of the fibers are preganglionic sympathetic and synapse directly with the cells of the medulla.
Fourman, J., and Moffat, D. B., The Blood Vessels of the Kidney, Blackwell, Oxford, 1971. Renal vasculature in relation to function.
Graves, F. T., The Arterial Anatomy of the Kidney, Wright, Bristol, 1971. Anatomical studies as a basis for surgical technique.
29-1 Which level of the vertebral column would be crossed by a line joining the hili of the kidneys?
29-2 How may the kidney be approached surgically from the posterior side?
29-3 Where would a perinephric abscess be situated?
29-4 List some congenital anomalies of the kidneys.
29-5 Where is a ureter likely to be obstructed?
29-6 To where is the pain of renal colic referred?
29-7 The suprarenal glands are found posterior to which structures?
29-8 What are the cortical and chromaffin systems?
Figure 29-1 Coronal section of a kidney. (From Yokochi, C, Photographic Anatomy of the Human Body, Igaku Shoin, Ltd., Tokyo, 1971.)
Figure 29-2 Anterior relations of the kidneys. The areas covered by peritoneum are shown in blue. In addition to the renal vessels, the origins of the celiac, superior mesenteric, gonadal (testicular or ovarian), and inferior mesenteric arteries are included, as are the terminations of the gonadal veins.
Figure 29-3 Intravenous pyelogram. Note the calices, some of which are seen from the side and others end-on, and the pelves of the ureters, which differ in shape and level. (Courtesy of Sir Thomas Lodge, Sheffield, England.)
Figure 29-4 Renal and related vessels. A large area is drained by the left renal vein, which receives tributaries from the back, abdominal wall, diaphragm, suprarenal gland, and gonad.
Figure 29-5 Horizontal section through the abdomen to show renal fascia, as described in the text. The arrow indicates the lumbar approach to the kidney. Other features shown include the rectus sheath. (Cf. fig. 25-6.) See also fig. 40-1. (After Symington.)
Figure 29-6 Arterial segments of right kidney. The left is similar. (After Fourman and Moffat.) Interpretation of the posterior segment as two units (upper dorsal and lower dorsal) would provide a total of six arterial segments. The relationship between these and the four to nineteen lobes of the kidney has been examined in detail by Inke (in Vidrio, E. A., and Galina, M. A., eds., Advances in the Morphology of Cells and Tissues, Liss, New York, 1981, pp. 71-78).