Renal Anatomy - applied aspects

A comprehensive anatomical perspective of the renal anatomy and its applied aspects.

1. RENAL ANATOMY Dr. Manoj Kumar Deepak, M.S Resident Urology SRM Medical college and hospital

2. GENERAL ANATOMY OF THE KIDNEYS Paired, bean-shaped organs located on either side of the vertebral column in the retroperitonum . Infront of the 11 th & 12 th rib Right kidney is lower than the left.

3. The kidney is related anteriorly to the abdominal viscera and posteriorly to the osteomuscular area. In the recumbent position, the kidneys may extend from T12 to L3 , but in the erect position extend from L1 to L4 . The kidneys changes position during different phases of respiration. They move inferiorly approximately 3 cm (one vertebral body) during inspiration and during changing body position

4. Coverings of kidneys The kidneys are surrounded by a smooth, tough fibrous capsule , which is easily removed under normal conditions. Perirenal fat : adipose tissue lies outside the fibrous capsule it extends into the renal hilum, into the space – a.k.a renal sinus.

5. R enal ( Gerota ) fascia – It covers kidneys and adrenals, it continues medially to fuse with the contralateral side This fascia extends inferomedially along the abdominal ureter as a periureteral fascia. It is closed superiorly and laterally - anatomic barrier to the spread of malignancy and a means of containing perinephric fluid collections. open inferiorly, perinephric fluid collections can track inferiorly into the pelvis without violating the Gerota fascia.

6. PARA RENAL FAT Para renal fat is a layer of adipose tissue, the occupies the retroperitoneum , which is most obvious posteriorly and represents the extraperitoneal fat of the lumbar region. It is necessary to main the position of the kidney. In thin young females devoid of para renal fat, Nephroptosis can occur. POINT TO REMEMBER IN PERCUTANEOUS PUNCTURE: Nephroptosis can cause difficulty in establishing access.

7. SIZE Length: 10-12 cm Width: 5-7.5 cm Thickness: 2.5-3.0 cm Approximate weight: 135 g in women and 150 g in men.

8. Each kidney has two surfaces ( anteriolateral and posteromedial) , two borders (lateral and medial), and two poles (superior and inferior.)

9. 1a 3 2 1b

10. SURGICAL ANATOMY OF THE KIDNEYS POINTS TO REMEMBER DURING PERCUTANEOUS PUNCTURE This brings the upper pole calyces medial and superficial (dorsal) in relation to the lower pole calyces, T he lower pole of the kidney lies laterally and anteriorly relative to upper pole.

11. ANTERIOR RELATIONS OF THE RIGHT KIDNEY The anterior surface of the right kidney is related to : Right adrenal gland Liver Second part of duodenum - needs to be mobilized to reach the hilum on the right side Ascending colon Hepatic flexure of the colon

12. ANTERIOR RELATIONS OF THE LEFT KIDNEY The anterior surface of the left kidney is related to: Left adrenal gland Pancreas Splenic vessels Stomach Spleen Duodenojejunal flexure Ligament of Treitz Inferior mesenteric vein Descending colon Splenic flexure of the colon Loops of jejunum

13. POSTERIOR RELATIONS OF THE KIDNEYS The posterior surfaces of the kidneys are related to: Psoas muscles Transversus abdominis muscles Quadratus lumborum muscles Diaphragm 12th thoracic nerves Iliohypogastric nerves Ilioinguinal nerves Subcostal vessels

14. Anterior layer of thoracolumbar (lumbodorsal) fascia Transversalis fascia Pararenal fat 11th and 12th ribs Pleurae Posterior layer of Gerota's fascia Perirenal fat Medial and lateral arcuate ligaments of the diaphragm

15. Anatomic relations of the kidneys. Posterior relations to the muscles of the posterior body wall and ribs. Relations to the pleural reflections and skeleton posteriorly.

16. Therefore percutaneous access to the collecting system is usually performed through a renal pyramid into a calyx to avoid these columns of Bertin containing larger blood v essels

17. The lateral border of the kidney is related to : the perirenal fat, Gerota's fascia, and Pararenal fat. L ateral contour may have a focal renal parenchymal bulge known as a dromedary hump, - no pathological significance

18. Medial border In the medial border of each kidney there is a vertical fissure called the renal porta or hilum . The concavity of the hilum is continuous with the renal sinus . The renal arteries and nerves enter through the renal hilum Veins, lymphatics, and proximal ureter exit through it. The renal pelvis most commonly lies posterior to the renal vessels

19. Within the renal sinus is the intra-renal pelvis , a funnel- shaped sac formed by the widely expanded portion of the proximal ureter and by the junctions of the major calices. In some instances the renal pelvis is small, lacks an extrarenal portion, and is located entirely within the renal parenchyma.

20. The UPPER POLE of each kidney is related to its associated adrenal gland, separated from it only by a thin diaphragm of connective tissue originating from the fascia of Gerota, which totally envelops each adrenal. The right and left adrenal glands are located superomedially at the front of the upper part of each kidney. The LOWER POLE is occasionally located close to the lumbar triangle. Associated with the psoas medially quadratus lumborum and transversus abdominis laterally

21. Gross and microscopic anatomy Pale outer cortex Dark inner medulla M edulla is divided into 8 to 18 striated, conically shaped areas called renal pyramids A pex of the pyramids forms the renal papilla , and each papilla is cupped by an individual minor Calyx

22. Cortex extends downward between the individual pyramids to form the columns of Bertin Interlobar arteries traverse these columns of Bertin Pyramids and their associated cortex form the lobes of the kidney.

23. INFUNDIBULUM CALYCEAL ANATOMY

24. If only one papilla drains into a minor calyx, it is described as a simple calyx. T wo or more papillae entering the calyx, it is termed a compound calyx. There are 5 to 14 minor calyces in each kidney There are three calyceal groups: the upper, middle, and lower . Compound calyces are the rule in the upper calyceal group , are common in the lower calyceal group, and are rare in the middle calyceal group. The minor calyces, either directly or after coalescing into major calyces, drain by infundibula into the renal pelvis The compound calyces of the poles of the kidney are oriented facing their respective poles. The middle calyces typically are arranged in a series of paired anterior and posterior calyces The simple calyces usually come in pairs, one facing anteriorly and one facing posteriorly.

25. In about two thirds of kidneys, there are two major calyceal systems—an upper and lower one—and the middle calyces drain into either or both systems. In the other one third of kidneys, the middle calyx drains into the pelvis direcly or via an infundibulum. Drainage of the upper pole into the renal pelvis is by a single midline infundibulum in most kidneys. Drainage from the lower pole is via a single infundibulum in about one half of kidneys and otherwise.

26. An important consideration for percutaneous renal surgery is determining the anterior-posterior orientation of the calyces to establish access. T he distinction pertains to the middle and lower calyceal system, which contains (in almost all middle systems and approximately one half of the lower system) paired anterior and posterior minor calyces. Paired anterior and posterior calyces usually enter at about 90 degrees from each other. The relative medial-lateral orientation (on anterior-posterior radiography) is determined by the relationship of this 90-degree unit to the frontal plane of the kidney.

27. In a Brödel -type kidney, this unit is rotated anteriorly , such that the posterior calyces are about 20 degrees behind the frontal plane and the anterior calyces are 70 degrees in front of the frontal plane. The posterior calyces are lateral , and the anterior calyces are medial in this case. The Hodson-type kidney is the opposite; the calyceal pairs are rotated posteriorly, with the posterior calyces 70 degrees behind the frontal plane and appearing medial and the anterior calyces 20 degrees in front of the frontal plane and appearing lateral. Most

28. R ight kidneys have a Brödel -type orientation (posterior calyces are lateral), and most left kidneys have a Hodson-type orientation. Because variation is considerable, the mediolateral orientation of the calyces on anteroposterior radiography cannot be used to reliably determine the optimal calyx for entry, and additional maneuvers are required to determine the exact calyceal anatomy.

29. One reliable anatomic distinction is that the upper calyceal group is situated in a mediolateral orientation in 95% of kidneys, in contrast with the anteroposterior orientation of the middle and lower calyceal groups in 100% and 95% of kidneys . This means that most calyces of the upper pole are suitable for percutaneous access from the posterior approach, whereas care must be taken to select a posterior minor calyx in the middle and lower groups. Within the lower calyceal group, the most inferior calyx is usually anterior, but the next most cephalad calyx is usually posterior.

30. The functional unit of the kidney is the nephron. Approximately 0.4 to 1.2 million nephrons are found in each adult kidney. The nephron consists of a glomerulus, (capillary tuft) surrounded by epithelial cells and the thin, fibrous Bowman capsule. The filtrate passes into the Bowman space and then into the proximal convoluted tubule , through the thin and thick limbs of the loop of Henle , to the macula densa adjacent to the glomerulus, and into the distal convoluted tubule. It then enters the collecting tubules and the ducts of Bellini. MICROSCOPIC ANATOMY

31. ARTERIAL S UPPLY The paired renal arteries : originate from the lateral wall of the aorta just below the origin of the SMA between the L1 and L2 vertebrae. The origin of the longer right renal artery is more posterior than the left. Arising from each renal artery are before its trifurcation are two small arteries: the inferior suprarenal artery the artery for the renal pelvis and proximal ureter.

32. Segmental branches of the right renal artery demonstrated by renal angiogram (A) and corresponding diagram (B).

33. Each artery reaching the hilum divides into anterior and posterior divisions in relation to the renal pelvis. Furthermore, the five branches of each renal artery participate in the formation of four renal segments: apical(superior), anterior (subdivided into superior and inferior), posterior, and basilar (inferior)

34. Typical segmental circulation of the right kidney, shown diagrammatically. Notethat the posterior segmental artery is usually the first branch of the main renal artery, and extends behind the renal pelvis.

35. The intrarenal course and relation to the anterior calices of the apical, basilar, and anterior segmental arteries. Note the short length of the apical branch. The posterior branch is shown by a broken line.

36. The branch of the renal artery supplying the posterior segment of the kidney passes along the posterior surface of the renal pelvis and then divides into smaller branches that course between the posterior calices. The apical, basilar, and anterior branches are shown by broken lines.

37. BRÖDEL'S LINE Relatively avascular area of the kidney. L ocated slightly behind the convex border at the posterior half of the kidney It marks the junction of the area supplied by the anterior and posterior divisions of the renal artery. Incision in this area will permit removal of a stone within the renal calices with minimal damage. ( Ana tropic pyelolithotomy)

38. Scheme of the anterior and posterior branches of the renal artery, in a horizontal section of the kidney. The "avascular" line is the region of overlap between the anterior and posterior branches, situated posterolaterally rather than laterally because of the wider distribution of the anterior branches.

39. Avascular plane of kidney.

40. Each renal arteriole is an “end-artery,” For this reason, renal arterial vascular injury must be avoided to prevent loss of renal function. The potential for arterial injury is least in Brödel’s line Corticomedullary jn Columns od bertin Pyramids

41. Multiple renal arteries supply one renal segment while accessory arteries supply only part of the segment. It is advisable to ligate only the accessory arteries. An accessory artery of the lower pole may produce ureteric obstruction with secondary hydronephrosis. Ligation of an accessory renal artery can result in the production of an area of infarction of variable size, though often small. Renovascular hypertension may occur as a sequelae of the ischemia.

42. Schematic drawings of accessory renal arteries. A. Right kidney. B. Leftkidney. RK, right kidney; LK, left kidney; RU, right ureter; LU, left ureter; ROA, right ovarian artery; LOA, proximal part of the left ovarian artery; ROV, right ovarian vein; A, aorta; IVC, inferior vena cava; RARA, right accessory renal artery; LARA, left accessory renal artery.

43. Venous drainage The kidney is drained by several veins which together form the renal vein. Left renal vein Right renal vein longer shorter

44. L ymph a tics Follow the blood vessels and form large lymphatic trunks. The trunks exit through the renal sinus receiving communicating lymphatics from the renal capsule and perinephric fat. Lymphatics from the renal pelvis and upper ureter communicate with others at the renal hilum.

45. Regional lymphatic drainage of the right kidney. Green nodes, anterior; black nodes, posterior. Solid lines, anterior lymphatic channels; dashed lines,posterior lymphatic channels. Arrow leads to thoracic duct. The lymphatics of the right kidney drain into lymph nodes located between the IVC and the aorta, lateral paracaval nodes, and anterior and posterior inferior vena caval lymph nodes. They also drain upward toward the right diaphragm, and downward to the common iliac lymph nodes. Also into the thoracic duct or crossing the midline into the left lateral aortic lymph nodes.

46. Regional lymphatic drainage of the left kidney. Green nodes, anterior; black nodes, posterior. Solid lines, anterior lymphatic channels; dashed lines, posterior lymphatic channels. Arrows lead to thoracic duct. The lymphatics of the left kidney drain into the lateral paraaortic lymph nodes and anterior and posterior aortic lymph nodes. to the diaphragm and downward to lymph nodes associated with the inferior mesenteric artery.

47. INNERVATION The kidneys characteristically exhibit a very rich network of neural elem e n ts that originate at the celiac ganglion, aorticorenal plexus, and intermesenteric plexuses. These elements intermingle, form plexuses, and follow the renal artery. Thoracic nerves T10 to L1 participate in the innervation of the kidney. They receive pain fibers from the renal pelvis and proximal ureter that enter the spinal cord at those levels of the spinal nerves. The renal nerves have a vasomotor function. The right and left vagus nerves participate in the formation of the renal plexus. The renal plexus gives branches to the ureteric and gonadal plexuses.

48. Point to remember before percutaneous / open renal surgery. Nephroptosis can occur, especially in thin women with a paucity of perirenal fat . In such cases, the kidney not only descends but also rotates anteriorly. This can be troublesome during percutaneous punctures with the patient in a prone position. The position of right kidney The longitudinal axis of the kidneys from the vertical and the rotation of the kidney, t his brings the upper pole calyces medial and superficial (dorsal) in relation to the lower pole calyces,

49. The pleura can be punctured during entry into the upper pole. (Supra costal) The ribs curve inferiorly from medial to lateral, such that more portions of the kidney can be approached medially. Both the liver and spleen can extend lateral to the kidneys and are therefore at risk for injury with a lateral puncture into the kidney The ascending and descending colon can be lateral or even posterior to the right and left kidneys. Any organ can be injured with a misdirected or excessively deep puncture . Avoid injury to the 11th and 12th intercostal nerves , not only to avoid postoperative paresthesias and neuralgias, but also to avoid postoperative bulging from partial paralysis of the muscles involved.

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