Renal Anatomy

Renal Anatomy Renal Anatomy and Physiologyand Physiology

By: Wong Ann Cheng By: Wong Ann Cheng MD (UKM) MRCPCH (UK)MD (UKM) MRCPCH (UK)

Renal Anatomy and Renal Anatomy and Physiology Physiology

Macroscopic Macroscopic anatomyanatomy EmbrologyEmbrology Gross Gross Procedures Procedures InvestigationsInvestigations

Microscopic Microscopic anatomyanatomy GlomerularGlomerular Tubular Tubular

PhysiologyPhysiology Excretory functionExcretory function

Nitrogenous metabolic Nitrogenous metabolic waste: urea, uric acid, waste: urea, uric acid, creatcreat

Homeostatic functionHomeostatic function Water and salt Water and salt

regulationregulation Renin angiotensin Renin angiotensin

mechanismmechanism Acid/ base balanceAcid/ base balance

Endocrine functionEndocrine function ErythropoeitinErythropoeitin Prostaglandin Prostaglandin Calcitrol Calcitrol

EmbrologyEmbrology

Early development and evolution

Pronephros

Mesonephros

Metanephros

Ascent and abnormalities

Metanephros – Metanephros – definitive kidneydefinitive kidney The metanephros or The metanephros or

definitive kidney of definitive kidney of higher vertebrates, higher vertebrates, begins when the begins when the metanephric ducts metanephric ducts (ureteric buds) sprout (ureteric buds) sprout from the distal end of from the distal end of the mesonephric duct at the mesonephric duct at about 5 weeks.about 5 weeks.

The ureteric buds induce The ureteric buds induce intermediate mesoderm intermediate mesoderm in the sacral region to in the sacral region to form a metanephric form a metanephric blastema which forms blastema which forms the glomeruli and the glomeruli and tubules of the nephrons.tubules of the nephrons.

Evolution of the Kidneys: Evolution of the Kidneys: MetanephrosMetanephros

The ureteric buds bifurcate again and The ureteric buds bifurcate again and again to form the calyces and collecting again to form the calyces and collecting duct system of the definitive kidney.duct system of the definitive kidney.

The kidneys begin producing urine by The kidneys begin producing urine by week 12, and it adds to the volume of week 12, and it adds to the volume of the amniotic fluid. The fetus drinks this the amniotic fluid. The fetus drinks this fluid fluid in uteroin utero..

The fetal kidneys are not responsible for The fetal kidneys are not responsible for excretion as the placenta serves this excretion as the placenta serves this functionfunction

Ascent of Ascent of the the

KidneysKidneys

In the 6In the 6thth week the kidneys begin to ascend from the sacral week the kidneys begin to ascend from the sacral region to their position in the upper abdomen.region to their position in the upper abdomen.

The metanephric ducts elongate and become the ureters.The metanephric ducts elongate and become the ureters. As the kidney ascends it receives new segmental arteries As the kidney ascends it receives new segmental arteries

from the aorta and loses those vessels below (“climbing a from the aorta and loses those vessels below (“climbing a ladder”). Thus sometimes there is more than one renal ladder”). Thus sometimes there is more than one renal artery.artery.

Sometimes one kidney fails to ascend => pelvic kidneySometimes one kidney fails to ascend => pelvic kidney Sometimes the left and right kidneys become attached in Sometimes the left and right kidneys become attached in

the pelvis then the horseshoe kidney can’t ascend above the pelvis then the horseshoe kidney can’t ascend above the inferior mesenteric artery the inferior mesenteric artery

Position of Position of kidneyskidneys

Kidneys lie on the psoas muscle Kidneys lie on the psoas muscle beside the vertebral bodies.beside the vertebral bodies.

The diaphragm and 11The diaphragm and 11thth and 12 and 12thth ribs lie behind the upper half of ribs lie behind the upper half of each kidney.each kidney.

Therefore they move with breathingTherefore they move with breathing Left is higher than right (liver)Left is higher than right (liver) Upper poles T12Upper poles T12 Hilum is at L1/2Hilum is at L1/2 Lower poles at L3Lower poles at L3 Upper poles are more medial Upper poles are more medial

(psoas).(psoas). In the hilum:In the hilum:

Renal vein is the most anterior.Renal vein is the most anterior. Followed by renal artery & pelvis/ureterFollowed by renal artery & pelvis/ureter

Note that the left renal vein is Note that the left renal vein is longer .longer .

It crosses the aortaIs crossed by the SMAReceives left gonadal vein

Anterior relationsAnterior relations RightRight

AdrenalAdrenal Liver Liver

bare areabare area Hepatorenal Hepatorenal

pouchpouch

DuodenumDuodenum PancreasPancreas Right colic Right colic

flexureflexure JenunumJenunum

Left

Adrenal

Stomach

Spleen

Pancreas

Descending Colon

Jenunum

Macroscopic anatomyMacroscopic anatomy

Upper urinary tract

Renal

Lower urinary tract

Nephrology / Urology

Perirenal FatPerirenal Fat A layer of adipose tissue (fat) partially surrounds the kidney. A layer of adipose tissue (fat) partially surrounds the kidney.

It is usually a radilogy finding but occassional a tumor can arise from it.It is usually a radilogy finding but occassional a tumor can arise from it.

Renal CapsuleRenal Capsule The thin but tough covering of the kidney. It helps protect the kidney. The thin but tough covering of the kidney. It helps protect the kidney.

During a kidney biopsy, may feel a "pop" as the needle goes through the renal During a kidney biopsy, may feel a "pop" as the needle goes through the renal capsulecapsule

Renal CortexRenal Cortex The outer shell of the kidney between the The outer shell of the kidney between the renal capsulerenal capsule and the and the renal medullarenal medulla. . The renal cortex contains the The renal cortex contains the renal corpusclesrenal corpuscles (particularly the glomeruli) and (particularly the glomeruli) and most of the most of the renal tubulesrenal tubules (except for the (except for the loop of loop of HenleHenle). It is about 1 centimeter ). It is about 1 centimeter thick and also goes down between the thick and also goes down between the renal pyramidsrenal pyramids. Many kidney diseases . Many kidney diseases affect the affect the glomeruliglomeruli so the goal of a kidney biopsy is to sample this area. so the goal of a kidney biopsy is to sample this area.

Renal MedullaRenal Medulla The innermost area of the kidney. It is separated into 8 to 18 cone-shaped The innermost area of the kidney. It is separated into 8 to 18 cone-shaped sections called the medullary pyramids. If the biopsy needle goes in too far, you sections called the medullary pyramids. If the biopsy needle goes in too far, you may only get medulla and the biopsy will likely have to be repeated.may only get medulla and the biopsy will likely have to be repeated.

Medullary PyramidMedullary Pyramid An important part of the inner kidney. It consists primarily of collecting tubules An important part of the inner kidney. It consists primarily of collecting tubules as well as loops of Henle. The base of the medullary pyramid is next to the as well as loops of Henle. The base of the medullary pyramid is next to the cortex and it tapers to form the renal papillae. There are between 8 to 18 cortex and it tapers to form the renal papillae. There are between 8 to 18 medulla pyramids in each kidney.medulla pyramids in each kidney.

CalyxCalyx An extension of the renal pelvis that surrounds the renal papillae. It collects An extension of the renal pelvis that surrounds the renal papillae. It collects urine from the papillary ducts. Several minor calyces drain into a major calyx urine from the papillary ducts. Several minor calyces drain into a major calyx and then onto the renal pelvis.and then onto the renal pelvis.

Renal PelvisRenal Pelvis The area where the urine collects before entering the ureters. Two or three The area where the urine collects before entering the ureters. Two or three major calices come together to enter the renal pelvis. Cancers and kidney major calices come together to enter the renal pelvis. Cancers and kidney stones can form in renal pelvis and cause blood to be lost in the urine.stones can form in renal pelvis and cause blood to be lost in the urine.

Renal SinusRenal Sinus A cavity in the kidney that contains the calices and the renal pelvis. It also A cavity in the kidney that contains the calices and the renal pelvis. It also contains the blood vessels, nerves, and fat.contains the blood vessels, nerves, and fat.

Retroperitoneal organ Retroperitoneal organ Weight: 150gm each Weight: 150gm each Size: ~clenched fist sizeSize: ~clenched fist sizeLocationLocation

Right: hilum at L1-2Right: hilum at L1-2Left: hilum at L1Left: hilum at L1

Divided into cortex and medullaDivided into cortex and medullaEach ~1million unit nephrons and kidney Each ~1million unit nephrons and kidney cannot regenerate new nephrons.cannot regenerate new nephrons.

Physiologic anatomyPhysiologic anatomy

Two Paired Organs: Early in pregnancy, the kidneys become two distinct but paired organs. (1 in 1,000) only one kidney develops called congenital agenesis.

Shaped Like Beans: The kidneys are bean shaped. (1 in 400), the two kidneys fuse into a single horseshoe kidney Located in Your Lower Back: The kidneys lie in the retroperitoneum on either side of the spine. Some people are born with ectopic kidney, not proper location.

Roughly the Size of Your Fist: On the average, the kidneys are about 11-12 cm in length, 7-8 cm wide, 2-3 cm thick and weigh about 1/4 to 1/3 pound each. If large, it suggests congestion or inflammation. If small, it suggests scarring.

Microscopic anatomyMicroscopic anatomy

Total blood flow ~25% cardiac output.(1.2L/min)Total blood flow ~25% cardiac output.(1.2L/min)Renal Renal

arteryarterysegmentalsegmentalinterlobarinterlobararcuatearcuateinterlobulinterlobulararafferentafferentGlomerulusGlomerulusefferentefferentperitubular (vasa peritubular (vasa recta)recta)veinsveins

2 capillary beds2 capillary bedsHigh presure systemHigh presure system

hydrostatic pressure 60mmHg minus (32mmHg hydrostatic pressure 60mmHg minus (32mmHg oncotic pressure + 18 mmHg bowman hydrostatic oncotic pressure + 18 mmHg bowman hydrostatic pressure)pressure)

Renal cortex receives the most of the blood flow.Renal cortex receives the most of the blood flow.Renal medulla only receives 1-2% total blood flowRenal medulla only receives 1-2% total blood flow

Renal blood supplyRenal blood supply

SubstanceSubstance Mol wtMol wt FilterabilityFilterability

H2OH2O 1818 1.01.0

NaNa 2323 1.01.0

GluGlu 180180 1.01.0

InulinInulin 5 5005 500 1.01.0

MyoglobinMyoglobin 17 00017 000 0.750.75

Albumin Albumin 69 00069 000 0.0050.005

GFR depends onGFR depends on

Starling force net pressureStarling force net pressure

1= capillary hydrostatic 1= capillary hydrostatic pressure.pressure.

2= bowman capsule2= bowman capsule

hydrostatic pressurehydrostatic pressure

3= capillary oncotic 3= capillary oncotic pressurepressure

GFR depends onGFR depends on

1.1. Glomerular permeabilityGlomerular permeability

-capillary and bowman capsule endothelium, glomerular -capillary and bowman capsule endothelium, glomerular basement mambrane. basement mambrane.

2. Number of functioning glomeruli and total capillary 2. Number of functioning glomeruli and total capillary surface areasurface area

3. Glomerular capillary plasma flow3. Glomerular capillary plasma flow

ultrafiltrate: plasma minus protein/fatultrafiltrate: plasma minus protein/fat

Use of clearance method to Use of clearance method to quantify kidney functionquantify kidney function

The rates at which different The rates at which different substance are cleared from plasma substance are cleared from plasma provide a useful way of quantifying provide a useful way of quantifying the effectiveness of which the kidney the effectiveness of which the kidney excrete various substancesexcrete various substances

Renal clearance of a Renal clearance of a substancesubstance

Volume of plasma completely cleared of Volume of plasma completely cleared of the substance by the kidney per unit timethe substance by the kidney per unit time

Provides a useful way to quantify the Provides a useful way to quantify the excretory function of the kidneysexcretory function of the kidneys

Can be used to quantify the rate at which Can be used to quantify the rate at which blood flow through the kidneys as well as blood flow through the kidneys as well as the basic function of the kidney, the basic function of the kidney, glomerular filtration rate, tubular glomerular filtration rate, tubular reabsorption and tubular secretionreabsorption and tubular secretion

Cs x Ps = Us x VsCs x Ps = Us x Vs

Cs = clearance rate of a substance sCs = clearance rate of a substance s Ps = plasma concentration of the Ps = plasma concentration of the

substancesubstance V = urine flow rateV = urine flow rate Us = urine concentration of the Us = urine concentration of the

substancesubstance

Cs = Us x V / PsCs = Us x V / Ps

Renal clearance of a substance is Renal clearance of a substance is calculated from the urinary calculated from the urinary excretion rate (Us x V) of the excretion rate (Us x V) of the substance divided by its plasma substance divided by its plasma concentrationconcentration

Inulin clearanceInulin clearance

Can be used to estimate GFRCan be used to estimate GFR Substance existed that was freely Substance existed that was freely

filtered, not absorped or secreted by filtered, not absorped or secreted by the renal tubules, then the rate at the renal tubules, then the rate at which the substance was excreted in which the substance was excreted in the urine (Us x V) is equal the rate at the urine (Us x V) is equal the rate at which the substance was filtered by which the substance was filtered by the kidneys (GFR x Ps)the kidneys (GFR x Ps)

GFR x Ps = Us x VGFR x Ps = Us x V

GFR = US x V / Ps = CsGFR = US x V / Ps = Cs

Inulin – polysaccharide molecule Inulin – polysaccharide molecule which molecular rate of 5200which molecular rate of 5200

Not produced in the bodyNot produced in the body Found in the roots of certain plants.Found in the roots of certain plants. Must be administered IV to a patient Must be administered IV to a patient

to measure GFRto measure GFR

Other substances used to Other substances used to estimate GFRestimate GFR

Radioactive iothalamateRadioactive iothalamate CreatinineCreatinine

By product of skeletal muscle By product of skeletal muscle metabolismmetabolism

Present in plasma at relatively constant Present in plasma at relatively constant concentrationconcentration

Does not require IV infusionDoes not require IV infusion

Creatinine clearanceCreatinine clearance

Most widely used method for estimating Most widely used method for estimating GFR clinicallyGFR clinically

Creatinine not a perfest marker for GFRCreatinine not a perfest marker for GFR A small amount is excreted by the tubulesA small amount is excreted by the tubules The amount of creatinine excreted in the urine The amount of creatinine excreted in the urine

slightly exceeds the amount filteredslightly exceeds the amount filtered Overestimation of the plasma concentrationOverestimation of the plasma concentration

The creatinine clearance provides a The creatinine clearance provides a reasonable estimate of the GFRreasonable estimate of the GFR

FormulaFormula GFRGFR ((total plasma volume/min from capillary to bowman capsuletotal plasma volume/min from capillary to bowman capsule)) 38× Ht( cm )/ plasma Creatinine (mcmol/L)38× Ht( cm )/ plasma Creatinine (mcmol/L)

Normal adult- 120ml/min/1.73mNormal adult- 120ml/min/1.73m22

Creat. clearanceCreat. clearance ((plasma volume removed /min by kidneyplasma volume removed /min by kidney)) Urine creatinine (mmol/L) × Urine volume (ml/min)/Urine creatinine (mmol/L) × Urine volume (ml/min)/

plasma creatinine(mmol/L) plasma creatinine(mmol/L)

Normal:Normal: ♂ 90-140ml/min♂ 90-140ml/min

♀ ♀ 80-125ml/min80-125ml/min

Creatinine clearanceCreatinine clearance

Physiologic control of GFR and Physiologic control of GFR and Renal blood flowRenal blood flow

1.1. Sympathetic NS Sympathetic NS activation: all blood activation: all blood vessels are richly vessels are richly innervated.innervated.

Most important during Most important during severe acute severe acute disturbancesdisturbances

2.2. Hormonal (see table) Hormonal (see table)

Hormone or Hormone or autocoidautocoid

Effect on GFREffect on GFR

NorepinephrinNorepinephrinee

↓↓

EpinephrineEpinephrine ↓↓

EndothelinEndothelin ↓↓

Angiotensin IIAngiotensin II ↔ ↔ (prevents ↓)(prevents ↓)

Endothelial Endothelial derived NOderived NO

↑↑

Prostaglandin Prostaglandin ↑↑

Autoregulation of GFR & Renal Autoregulation of GFR & Renal blood flowblood flow

Renin Angiotensin Renin Angiotensin Aldosterone SystemAldosterone System

Powerful mechanism for controlling Powerful mechanism for controlling pressurepressure

Renin: small protein released by kidneys Renin: small protein released by kidneys when arterial pressure falls too lowwhen arterial pressure falls too low Synthesized and stored in an inactive form Synthesized and stored in an inactive form

called prorenin in the JG cells of the kidneyscalled prorenin in the JG cells of the kidneys JG cells are modified smooth muscle cells JG cells are modified smooth muscle cells

located in the walls of the afferent arterioles located in the walls of the afferent arterioles immediately proximal to the glomeruliimmediately proximal to the glomeruli

Two principal effects of Two principal effects of Angiotensin II that can Angiotensin II that can

elevate APelevate AP Vasoconstriction –Vasoconstriction –

occurs rapidlyoccurs rapidly Intense in the Intense in the

arterioles and less arterioles and less extent in veinsextent in veins

Constriction in Constriction in arterioles increases arterioles increases peripheral resistance, peripheral resistance, raising APraising AP

Mild constriction in Mild constriction in veins promotes veins promotes increase venous return increase venous return to the heart, helping to the heart, helping the heart pump against the heart pump against increase pressureincrease pressure

Decreased excretion Decreased excretion of both salt and of both salt and water – slowly water – slowly increases the ECF increases the ECF volume, increases volume, increases AP over period of AP over period of hours and dayshours and days Even more powerful Even more powerful

than acute than acute vasoconstrictor vasoconstrictor mechanism in mechanism in eventually returning eventually returning AP back to normalAP back to normal

Two ways by which Two ways by which Angiotensin causes salt and Angiotensin causes salt and

water retentionwater retention Angiotensin acts directly on the Angiotensin acts directly on the

kidneys to cause salt and water kidneys to cause salt and water retentionretention

Angiotensin causes the adrenal Angiotensin causes the adrenal glands to secrete aldosterone, and glands to secrete aldosterone, and the aldosterone in turn increases the aldosterone in turn increases salt and water reabsorption by the salt and water reabsorption by the kidneys tubuleskidneys tubules

Procedure anatomyProcedure anatomy

Orientation and Orientation and surroundingssurroundings The medial border of each kidney is anterior to The medial border of each kidney is anterior to

the lateral border (psoas). Thus the coronal the lateral border (psoas). Thus the coronal plane of the kidney is at 30 degrees to the plane of the kidney is at 30 degrees to the coronal plane of the body.coronal plane of the body.Layers surrounding

the kidneyOutside the renal capsule is perirenal fat

Then is the renal fascia which also surrounds the adrenals

This is embedded in extraperitoneal fat (pararenal fat)

RENAL BIOPSY

Normal anatomy

The kidneys are paired organs that lie posterior to the abdomen, in the area of the lower back. The kidneys make urine, which is transported from the kidneys to the bladder by the ureters, long muscular tubes which connect the kidneys with the bladder.

Kidney transplant may be recommended for patients with kidney failure caused by:severe, uncontrollable high blood pressure (hypertension) infections diabetes mellitus congenital abnormalities of the kidneys other diseases which cause renal failure, such as autoimmune diseaseDonor kidneys are obtained from either brain-dead organ donors, or from living relatives or friends of the recipient.

Incision

While the patient is deep asleep and pain-free (general anesthesia), an incision is made in the lower right quadrant of the abdomen. The donor kidney is transplanted into the right lower pelvis of the recipient.

Procedure

The new kidney is sutured into place. The vessels of the new kidney are connected to the vessels leading to the right leg (the iliac vessels), and the ureter is sutured to the bladder.

Aftercare

In most cases, the recipient's native kidneys are left in place, and the transplanted kidney performs all the functions that both kidneys perform in healthy people. Kidney transplant recipients are required to take immunosuppressive medications for the rest of the lives, to prevent immune rejection of the transplanted organ.

Kidney StructureNumber of Kidneys: agenesis Shape of the Kidneys: horseshoe kidneyLocation of the Kidneys: ectopic kidney.

Finding Kidney Stones, Cysts, and MassesKidney Stones: The kidney ultrasound is a useful screening test for kidney stones. Not all kidney stones can be seen on ultrasound, but many can be. If a stone is causing ureter obstruction, there may be hydronephrosis. Ureter Obstruction: A kidney ultrasound is routinely ordered to rule out obstruction in kidney failure. Impeding the flow of urine can cause it to back up and dilate the ureters and kidneys. It should be noted that finding hydronephrosis doesn’t necessarily mean there is an obstruction.Kidney Cysts: The kidney ultrasound is very good at discovering kidney cysts, most of which are uncomplicated and incidental findings. Some cysts look complicated or complex and may represent infection, bleeding or cancer. People with polycystic kidney disease have multiple large cysts that replace normal tissue and destroys the kidneys. Kidney Masses: The ability of kidney ultrasound to detect a kidney mass depends on its size. It is very good for large masses (> 3 cm) but not so good for small tumors.

Signs of Kidney Chronic DiseaseKidney Size: On the average, the kidneys are about 11-12 cm in length, 7-8 cm wide, and 2-3 cm in thickness. If they are very small, it suggests significant scarring and irreversible damage. Thickness of the Cortex: The cortex is the outer shell of the kidney (about 1 cm in thickness) and contains all the glomeruli. If it particularly thin, it suggests chronic kidney disease and may make it hard to biopsy. If it is thick, it may mean inflammation and congestion. Echogenicity of the Cortex: Echogenicity refers to how the sound waves look when they bounce off something. It is often said that it is not normal if there is a lot of echogenicity (compared to the liver). In reality, it is not a very reliable indicator of kidney disease.

RENAL ULTRASOUND

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