Renal tract and Posterior Abdominal Wall

Question 1

What are the kidneys?

Answer 1

Reddish brown, bean shaped, has superior and inferior poles, anterior and posterior surfaces and lateral and medial margins.
10cm long, 5cm wide and 2.5-3cm thick (remember 2.5, 5, 10cm or 1, 2, 4 inches)
Perirenal fat, Renal fascia, external to renal fascia is the Pararenal fat. Fatty tissue keeps the kidneys in place.
Renal fascia sends out collagen bundles into the pararenal fat to the lumbar fascia.

Question 2

What is the location of the kidneys?

Answer 2

Retroperitoneal at T12-L3 vertebral level, right kidney lies more inferior than left kidney. Transpyloric plane passes through the hilum of the left kidney about 5 cm from the midline and superior pole of the right kidney that is about 2.5 cm lower than the left kidney.

Question 3

What are the relations of the kidneys?

Answer 3

Superior(posteriorly)- Diaphragm
Inferior (posteriorly)- Quadratus lumborum with subcostal, illioinguinal and illiohypogastric nerves passing posteriorly
Anterior to right kidney- liver with hepatorenal recess, duodenum and ascending colon
Anterior to the left kidney- stomach, spleen, pancreas, jejunum, and descending colon

Question 4

What is the macrostructure of the kidney?

Answer 4

Renal hilum – Renal artery enters and renal vein and renal pelvis leave the kidney
Renal pelvis - Flat, funnel shaped structure attached to the upper end of the ureter. Renal pelvis receives major calyces that are formed by the collection of minor calyces that are indented by a renal papilla.
On sectioning, the kidney has a pale outer region- the cortex- and a darker inner region- the medulla.
The medulla is divided into 8-18 conical regions, called the renal pyramids; the base of each pyramid starts at the corticomedullary border, and the apex ends in the renal papilla which merges to form the renal pelvis and then on to form the ureter.
The walls of the calyces, pelvis and ureters are lined with smooth muscle that can contract to force urine towards the bladder by peristalisis.
The cortex and the medulla are made up of nephrons; these are the functional units of the kidney, and each kidney contains about 1.3 million of them.

Question 5

What is the function of the kidneys?

Answer 5

Removal of waste products and excess water from the body.

Regulation of fluid, electrolyte and acid-base balance.

Hormones – Renin and Erythropoietin

Question 6

What are the nerves and vasculature of the kidneys?

Answer 6

The renal arteries arise at the level L1 and L2 IV disc . Right is longer and passes posterior to the IVC
Divide close to the hilum into five segmental arteries
Several renal veins drain each kidney and unite in a variable fashion to form the right and left renal veins. The right and left renal veins lie anterior to the right and left renal arteries. The longer left renal vein receives the left suprarenal vein, the left gonadal (testicular or ovarian) vein and drain into the IVC.
The nerves to the kidneys arise from the renal nerve plexus and consist of sympathetic and parasympathetic fibers. The renal nerve plexus is supplied by fibers from the abdominopelvic splanchnic nerves.

Question 7

What are the ureters?

Answer 7

25-30 cm long muscular ducts.
Form a connection between kidneys and the urinary bladder.
Ureters lie retroperitoneal and the abdominal parts adhere to the parietal peritoneum.
There are three constrictions in each ureter that are clinically important;
Junction of ureter and the renal pelvis
Pelvic brim
Entrance into the urinary bladder
The pelvic parts of the ureters run on the lateral walls of the pelvis, parallel to the anterior margin of the greater sciatic notch , opposite the ischial spine, they curve anteromedially, and enter the urinary bladder. The inferior ends of the ureters are surrounded by the vesical venous plexus . They pass obliquely through the muscular wall of the urinary bladder in an inferomedial direction

Surface marking of the ureter is a line joining a point 5 cm lateral to the L1 spinous process and the posterior superior iliac spine. The ureters occupy a sagittal plane that intersects the tips of the transverse processes of the lumbar vertebrae.

Question 8

What is the vasculature of the ureters?

Answer 8

Arterial branches to the abdominal portion of the ureter arise from the renal arteries.
The arterial supply to the pelvic parts of the ureters is variable, with ureteric branches extending from the common iliac, internal iliac, and ovarian arteries. The ureteric branches anastomose along the length of the ureter forming a continuous blood supply, although not necessarily effective collateral pathways. The most constant arteries supplying the terminal parts of the ureter in females are branches of the uterine arteries. The source of similar branches in males are the inferior vesical arteries.

Veins draining the abdominal part of the ureters drain into the renal and gonadal (testicular or ovarian) veins.
The venous drainage from the pelvic parts of the ureters generally parallels the arterial supply, draining to veins with corresponding names.

Question 9

What are the Adrenal (Suprarenal) glands?

Answer 9

located between the superomedial aspects of the kidneys and the diaphragm surrounded by perinephric fat and renal fascia by which they are attached to the crura of the diaphragm.
The pyramidal right gland is more apical (situated over the superior pole), lies anterolateral to the right crus of the diaphragm, and makes contact with the IVC anteromedially and the liver anterolaterally.
The crescent-shaped left gland is medial to the superior half of the left kidney and is related to the spleen, stomach, pancreas, and the left crus of the diaphragm.

Question 10

What is the Gross structure of the adrenals (suprarenals)?

Answer 10

Each gland has a hilum, where the veins and lymphatic vessels exit the gland
Arteries and nerves enter the glands at multiple sites.
Suprarenal glands are 4-5 cm apart, separated by IVC, right crus of the diaphragm, coeliac ganglion, coeliac trunk, SMA, and the left crus of the diaphragm.
Each suprarenal gland has two parts: the suprarenal cortex and suprarenal medulla ; Both are embryologically and functionally different
The adrenal cortex derives from mesoderm and secretes two types of steroids and androgens.
The adrenal medulla is a mass of nervous tissue permeated with capillaries and sinusoids that derives from neural crest cells associated with the sympathetic nervous system . The chromaffin cells of the medulla are related to sympathetic ganglion (postsynaptic) neurons in both derivation (neural crest cells) and function. These cells secrete catecholamines (mostly epinephrine) into the bloodstream in response to signals from presynaptic neurons.

Question 11

What are the adrenal hormones?

Answer 11

Adrenal cortex
Mineralocorticoid - Aldosterone, stimulates sodium and water uptake, and potassium excretion in the kidneys
Glucocorticoids - essential for stress response and protein, carbohydrate and fat metabolism
Androgens – oestrogen in females, testosterone in males

Adrenal medulla
Adrenaline and noradrenaline – fight or flight – both cause tachycardia, raised BP, sweating, bronchiolar dilation, pupillary dilation.
Dopamine – neurotransmitter - small amounts only, but the vast majority of dopamine is produced in the brain (e.g. substantia nigra)

Question 12

What is the nerve supply of the adrenal gland?

Answer 12

Nerve supply of the suprarenal gland is from the celiac plexus and abdominopelvic (greater, lesser, and least) splanchnic nerves. Myelinated presynaptic sympathetic fibers—mainly derived from the intermediolateral cell column (IML), or lateral horn, of gray matter of the spinal cord segments T10-L1—traverse both the paravertebral and the prevertebral ganglia, without synapse, to be distributed to the chromaffin cells in the suprarenal medulla.

Question 13

What is the Lymphatics of Kidneys, Ureters, and Suprarenal Glands?

Answer 13

The renal lymphatic vessels follow the renal veins and drain into the right and left lumbar (caval and aortic) lymph nodes. Lymphatic vessels from the superior part of the ureter may join those from the kidney or pass directly to the lumbar nodes. Lymphatic vessels from the middle part of the ureter usually drain into the common iliac lymph nodes, whereas vessels from its inferior part drain into the common, external, or internal iliac lymph nodes.
Lymphatic vessels from pelvic part of ureter pass primarily to common and internal iliac nodes

Question 14

What is the location of the urinary bladder?

Answer 14

The urinary bladder is a temporary reservoir for urine and varies in size, shape, position, and relationships according to its content and the state of neighboring viscera.
When empty, the adult urinary bladder is located in the lesser pelvis, lying partially superior to and partially posterior to the pubic bones. It is separated from these bones by the potential retropubic space (of Retzius) and lies mostly inferior to the peritoneum, resting on the pubic bones and pubic symphysis anteriorly and the prostate (males) or anterior wall of the vagina posteriorly .
The bladder is relatively free within the extraperitoneal subcutaneous fatty tissue, except for its neck, which is held firmly by the lateral ligaments of bladder and the tendinous arch of the pelvic fascia—especially its anterior component, the puboprostatic ligament in males and the pubovesical ligament in females.

Question 15

What is the structure of the bladder?

Answer 15

Apex of the bladder points toward the superior edge of the pubic symphysis when the bladder is empty.
The fundus or posterior surface of the bladder is opposite the apex, formed by the somewhat convex posterior wall.
The body of the bladder is the major portion of the bladder between the apex and the fundus. The fundus and inferolateral surfaces meet inferiorly at the neck of the bladder.
The ureteric orifices and the internal urethral orifice are at the angles of the trigone of the bladder . The ureteric orifices are encircled by loops of detrusor musculature that tighten when the bladder contracts to assist in preventing reflux of urine into the ureter.
The walls of the bladder are composed chiefly of the detrusor muscle. Toward the neck of the male bladder, the muscle fibers form the involuntary internal urethral sphincter.
Bladder bed. On each side, the pubic bones and fascia covering the levator ani and the superior obturator internus lie in contact with the inferolateral surfaces of the bladder . Only the superior surface is covered by peritoneum. Consequently, in males the fundus is separated from the rectum centrally by only the fascial rectovesical septum and laterally by the seminal glands and ampullae of the ductus deferentes . In females the fundus is directly related to the superior anterior wall of the vagina.

Question 16

What is the Arterial Supply and Venous Drainage of Bladder?

Answer 16

Branches of the internal iliac arteries. The superior vesical arteries supply anterosuperior parts of the bladder. In males, the inferior vesical arteries supply the fundus and neck of the bladder. In females, the vaginal arteries replace the inferior vesical arteries and send small branches to posteroinferior parts of the bladder. The obturator and inferior gluteal arteries also supply small branches to the bladder.
The veins draining blood from the bladder correspond to the arteries and are tributaries of the internal iliac veins.

Question 17

What is the innervation of the bladder?

Answer 17

Sympathetic fibers are conveyed from inferior thoracic and upper lumbar spinal cord levels to the vesical (pelvic) plexuses primarily through the hypogastric plexuses and nerves
Parasympathetic fibers from sacral spinal cord levels are conveyed by the pelvic splanchnic nerves and the inferior hypogastric plexus. The parasympathetic fibers are motor to the detrusor muscle and inhibitory to the internal urethral sphincter of the male bladder. Hence, when visceral afferent fibers are stimulated by stretching, the bladder contracts reflexively, the internal urethral sphincter relaxes (in males), and urine flows into the urethra.
The sympathetic innervation can cause the internal sphincter to contract, hampering the ability to urinate until parasympathetic inhibition of the sphincter occurs.
Sensory fibers from most of the bladder are visceral; reflex afferents follow the course of the parasympathetic fibers, as do those transmitting pain sensations (such as results from overdistension) from the inferior part of the bladder. The superior surface of the bladder is covered with peritoneum and is therefore superior to the pelvic pain line; thus pain fibers from the superior bladder follow the sympathetic fibers retrogradely to the inferior thoracic and upper lumbar spinal ganglia (T11-L2 or L3).

Question 18

What is posterior abdominal wall?

Answer 18

Five lumbar vertebrae and associated IV discs (centrally).
Posterior abdominal wall muscles, including the psoas, quadratus lumborum, iliacus, transversus abdominis, and oblique muscles (laterally).
Diaphragm, which contributes to the superior part of the posterior wall.
Fascia, including the thoracolumbar fascia.
Lumbar plexus, composed of the anterior rami of lumbar spinal nerves.
Fat, nerves, vessels (e.g., aorta and IVC), and lymph nodes.

Question 19

What are the nerves of the posterior abdominal wall?

Answer 19

The subcostal nerves (anterior rami of T12) arise in the thorax
The lumbar spinal nerves (L1-L5) pass from the spinal cord through the IV foramina inferior to the corresponding vertebrae, where they divide into posterior and anterior rami. The initial portions of the anterior rami of the L1, L2, and occasionally L3 spinal nerves give rise to white communicating branches (L. rami communicantes), which convey presynaptic sympathetic fibers to the lumbar sympathetic trunks.
The abdominal part of the sympathetic trunks (lumbar sympathetic trunks), consisting of four lumbar paravertebral sympathetic ganglia and the interganglionic branches that connect them, are continuous with the thoracic part of the trunks deep to the medial arcuate ligaments of the diaphragm.
lumbar plexus of nerves; femoral nerve (L2-L4), obturator nerve (L2-L4), lumbosacral trunk (L4, L5), ilioinguinal and iliohypogastric nerves (L1), genitofemoral nerve (L1, L2), lateral cutaneous nerve of the thigh.

Question 20

What are the vessels of the posterior abdominal wall?

Answer 20

The subcostal arteries arise from the thoracic aorta and distribute inferior to the 12th rib.
The abdominal aorta is approximately 13 cm in length. It begins at the aortic hiatus in the diaphragm at the level of the T12 vertebra and ends at the level of the L4 vertebra by dividing into the right and left common iliac arteries.
The common iliac arteries diverge and run inferolaterally, following the medial border of the psoas muscles to the pelvic brim. Here each common iliac artery divides into the internal and external iliac arteries. The internal iliac artery enters the pelvis. The external iliac artery follows the iliopsoas muscle. Just before leaving the abdomen, the external iliac artery gives rise to the inferior epigastric and deep circumflex iliac arteries, which supply the anterolateral abdominal wall.

Question 21

What are the relations of the abdominal aorta?

Answer 21

From superior to inferior, the important anterior relations of the abdominal aorta are the:
Coeliac plexus and ganglion
Body of the pancreas and splenic vein
Left renal vein
Horizontal part of the duodenum.
Coils of small intestine.

Question 22

What are the veins of posterior abdominal wall?

Answer 22

Veins of posterior abdominal wall are; Tributaries of the IVC, except for the left testicular or ovarian vein, which enters the left renal vein instead of entering the IVC
The IVC, has no valves except a non-functional one at its opening in the right atrium. IVC returns poorly oxygenated blood from the lower limbs, most of the back, the abdominal walls, and the abdominopelvic viscera. Blood from the abdominal viscera passes through the portal venous system and the liver before entering the IVC via the hepatic veins.
L5- T8, formed by the union of the common iliac veins. approximately 2.5 cm right of the median plane, inferior to the aortic bifurcation. IVC then ascends on the right side of the bodies of the L3-L5 vertebrae and on the right psoas major to the right of the aorta. The IVC leaves the abdomen by passing through the caval opening .

Question 23

What are the IVB (Inferior vena cava) tributaries?

Answer 23

The tributaries of the IVC correspond to the paired visceral and parietal branches of the abdominal aorta. The veins that correspond to the unpaired visceral branches of the aorta are instead tributaries of the hepatic portal vein. The blood they carry does ultimately enter the IVC via the hepatic veins, after traversing the liver.
The branches corresponding to the paired visceral branches of the abdominal aorta include the right suprarenal vein, the right and left renal veins, and the right gonadal (testicular or ovarian) vein. The left suprarenal and gonadal veins drain in the left renal vein.
Paired parietal branches of the IVC include the inferior phrenic veins, the 3rd (L3) and 4th (L4) lumbar veins, and the common iliac veins. The ascending lumbar and azygos veins connect the IVC and SVC, either directly or indirectly providing collateral pathways

Question 24

What are the LYMPHATIC VESSELS AND LYMPH NODES OF POSTERIOR ABDOMINAL WALL?

Answer 24

Lymphatic vessels and lymph nodes lie along the aorta, IVC, and iliac vessels.
The common iliac lymph nodes receive lymph from the external and internal iliac lymph nodes. Lymph from the common iliac lymph nodes passes to the right and left lumbar lymph nodes.
Lymph from the alimentary tract, liver, spleen, and pancreas passes along the celiac and superior and inferior mesenteric arteries to the preaortic lymph nodes (celiac and superior and inferior mesenteric nodes) scattered around the origins of these arteries from the aorta. Efferent vessels from these nodes form the intestinal lymphatic trunks, which may be single or multiple, and participate in the confluence of lymphatic trunks that gives rise to the thoracic duct .
The right and left lumbar (caval and aortic) lymph nodes lie on both sides of the IVC and aorta. These nodes receive lymph directly from the posterior abdominal wall, kidneys, ureters, testes or ovaries, uterus, and uterine tubes. They also receive lymph from the descending colon, pelvis, and lower limbs through the inferior mesenteric and common iliac lymph nodes. Efferent lymphatic vessels from the large lumbar lymph nodes form the right and left lumbar lymphatic trunks.

Question 25

What is the thoracic duct?

Answer 25

The inferior end of the thoracic duct lies anterior to the bodies of the L1 and L2 vertebrae between the right crus of the diaphragm and the aorta.
The thoracic duct begins with the convergence of the main lymphatic ducts of the abdomen, and a thin-walled sac or dilation, the cisterna chyli (chyle cistern) . Cisterna chyli vary greatly in size and shape. More often there is merely a simple or plexiform convergence at this level of the right and left lumbar lymphatic trunks, the intestinal lymph trunk(s), and a pair of descending thoracic lymphatic trunks, which carry lymph from the lower six intercostal spaces on each side.
The thoracic duct ascends through the aortic hiatus in the diaphragm into the posterior mediastinum, where it collects more parietal and visceral drainage, particularly from the left upper quadrant of the body. The duct ultimately ends by entering the venous system at the junction of the left subclavian and internal jugular veins (the left venous angle).