Kidneys Flashcards
What is the anatomical location of kidneys?
Retroperitoneal
Flank area
Renal Embryology
Kidneys usually develop by 15 weeks gest age in pelvis and then ascend to lumbar region.
Migration is not complete until 5-6 years old
Which muscles are posterior to the kidneys?
Psoas muscle, and Quadrates Lumbordum muscles.
What covers the kidneys?
Gerota’s Fascia
Which also covers the peritoneal fat, renal capsule and adrenal glands
What is the normal adult kidney measurement?
9-12 cm in length
4-6 cm in diameter
2.5-4 cm in depth (AP)
Neonatal kidney measurements?
3.5-5 cm in length
2-3 cm in diameter
1.5-2.5 cm in depth
What are the 3 distinct regions of the renal parenchyma?
Cortex, medulla (medullary pyramids) and renal pelvis
What is the pathway of urine through the collecting system?
Urinary sinus- minor calyces- major calyces- renal pelvis- ureter- bladder
What is the echogenicity of a normal kidney?
Renal cortex is homogenous and either isoechoic or hypoechoic to liver or spleen
Medullary pyramids are usually hypoechoic to anechoic in appearance.
Collecting system/ sinus appears highly echogenic due to fat and only becomes hypoechoic or anechoic when there is blockage
What is the anatomical relationship of the renal artery in respect to the IVC?
Right renal artery passes posterior to IVC
What is the anatomical relationship of the renal veins?
Right renal vein is shorter than left
Left renal vein courses anterior to aorta but posterior to SMA
*renal veins are inferior to renal arteries
What does the renal arterial vasculature consist of?
Renal artery, segmental artery, interlobar artery, arcuate artery, interlobular artery
What is the pathway of blood through the kidney?
Segmental arteries- interlobar a.- arcuate a.- interlobular a.- afferent arteriole- glomerular filtration- efferent arteriole- peritubular capillaries- interlobular v.- arcuate v.- interlobar v.- renal v.- IVC
What is the functional unit of the kidney?
Nephron
What is the excretory function of the kidney?
Removal of waste from blood by the glomerulus
What is the regulatory function of the kidney?
Balances fluid and electrolyte contents of blood through re-absorption and secretion by the renal tubules
Which components of blood are too large to pass through the nephron’s membrane?
Blood cells such as RBC, WBC, Platelets, and plasma proteins such as albumin and globulin.
What is Aldosterone?
Hormone secreted by adrenal glands.
Increases tubule permeability to increase reabsorption of sodium.
Adjusts fluid uptake in the event of dehydration and hemorrhage
Which is the most specific indicating lab function test for kidney dysfunction?
Serum Creatinine
What other lab function test are there for renal evaluation?
BUN- also rises with renal dysfunction
Uric Acid level- increases with renal failure and causes gout
Why do RBC increase when renal dysfunction is present?
Kidney secretes erythropoietin to stimulate RBC production from bone marrow in the presence of hypernephroma, RCC and renal cysts
What is the most common anomaly of the genitourinary tract?
Duplicate collecting system
1 in 157 adults
Most common in women
What types of duplicate collecting systems are there?
Incomplete: 2 pelvis, 1 ureter
Complete: 2 pelvis, 2 ureter * may become obstructed due to ureterocele
What is the sonographic appearance of duplicate collecting system?
Complete separation of normal renal sinus echodensities
Cause of isolated hydronephrosis
Can mimic cyst but cyst usually in cortex
What is prominent or hypertrophic column of Bertin?
Considered a variant
Double thickness of cortical tissue between 2 pyramids
can create or mimic a pseudocyst
Sonographic findings with column of Bertin
Renal sinus is clearly defined
Largest dimension is less than 3 cm
It is continuous or contiguous with the renal cortex
Echogenicity is close to that of the cortex
What is Dromedary Hump?
A variant
Bulging of the mid section of left kidney
Same echogenicity as cortex
What is horseshoe kidney?
Anomaly
Lower pole of kidneys are fused at the midline of body
1 in 400
IVP and CT are good for identification of horseshoe kidney in adjunct to ultrasound
What Is pelvic kidney?
Anomaly
Non-visualization of a kidney in renal fossa
Ectopic kidney. Failed to ascend to upper quadrant.
Note: transplanted kidneys are in the pelvis
What is Renal Agenesis?
Anomaly
No kidney formation.
Will have unilateral large kidney due to contra-lateral compensation
What is another name for Junctional Parenchymal Defect?
Fetal Lobation
Typically occurs on the anterior surface of the upper pole of kidney
What is Supernumerary Kidney?
Anomaly
Very rare
Complete duplication of kidney
Extra kidney with its own blood supply. Usually ectopically placed and shares ureter
What is crossed renal ectopia?
When a kidney ascends to the contralateral side.
You will see 2 kidneys on one side of abdomen and none on the other
One ureter crosses midline to enter other side of bladder
What is crossed fused renal ectopia?
Unilateral fused kidney
The developing kidneys fuse while in the pelvis and one kidney ascends to its normal position, carrying the other one with it across the midline
What is extrarenal pelvis?
An extra renal pelvis that lies outside the renal sinus.
Sonographically appears as a cystic collection medial to the renal hilum
What is posterior urethral valve?
Common cause of urinary obstruction in a male infant due to a flap of mucosa that has a slit-like opening in the opening of the area of the prostatic urethra. You will see a large bladder Hydroureter Hydronephrosis Possible urinoma
What is Renal Sinus Lipomatosis?
Excessive fatty infiltration of the renal pelvis associated with obesity, or Parenchymal atrophy
What are the indications for a Renal Ultrasound?
Hematuria Oligouria (scanty urine) Flank pain Increased serum creatinine Palpable mass in lumbar region Chronic UTI Obstruction of the GU tract such as nephrolithiasis
How does renal infection develop?
Secondary to respiratory infection, its prevalence can cause mortality. Usually originates from bladder and spreads to kidneys.
E-colimis the most common bacteria responsible for 85% UTI
Women are more susceptible due to shorter urethra.
Urinary stasis from voiding interference enhances bacterial growth (pregnancy, urolithiasis, benign prostatic hypertrophy- BPH)
Where can renal infection originate from?
Urethra, lymphatics, vascular.
Skin, bone and heart infections can disseminate to the nephron’s via blood
Who is more susceptible to renal infection and why?
Women due to shorter urethra
Women with increased sexual activity
Pregnancy due to increased pressure on bladder and ureters
What is Acute Pyelonephritis (APN), and what is its etiology?
Sudden Renal Plevis inflammation
Abrupt onset.
Usually caused by gram-negative bacilli from intestinal tract
Causes suppuration (puss)
Unilateral or bilat
Focal or diffused infection
Can lead to micro abcess formations in kidney
Associated with UTI
What are the clinical findings of APN?
Flank pain Fever and chills Urinary frequency Elevated WBC Dysuria (painful/difficult urination) Pyuria (puss in urine)
What are the sonographic findings of APN?
Kidneys may have normal appearance in early stages.
As infection progresses, the kidneys may show abnormal echopatterns (focal or diffused)
What is the focal appearance of APN?
Enlarged, hypoechoic kidney with absence of sinus echoes
What is the diffused appearance of APN?
Enlarged echogenic kidney due to multiple abscess
Cortex also becomes echogenic if there is abscess formation
The sinus will blend with the parenchyma
What is Acute Focal Bacterial Nephritis?
Focal wedge-shaped area or a hypoechoic renal lobe without renal enlargement
What is Emphysematous Pyelonephritis?
Emphysema- presence of air on tissue
Intrarenal gas accumulates causing a dirty ringdown reverberation artifact
Common in diabetes, immune-suppressed patients and those with UTI
What is Chronic Pyelonephritis (CPN)
And what causes it?
A silent, insidious, progressive disorder
From recurrent infections like UTI, obstructive lesions or vesico-ureteral reflux
Inflammation leads to scarring which can contribute to tubular dysfunction and parenchymal atrophy.
What is the clinical presentation of CPN?
Flank pain Oliguria HTN Foul smelling urine Slight increase in WBC Mild fever and chills Proteinuria (urine will be smoky)
What are the lab findings for CPN?
Poor renal function (decreased GFR)
Proteinuria
Increased blood creatinine
Increased BUN
What are the sonographic findings of CPN?
Kidneys will atrophy as the disease progresses (<8 cm)
Increased parenchymal echoes due to fibrosis
Echogenic Zone extends beyond normal areas of the sinus
What are other names for Renal Abscess?
Carbuncle
Perinephric Abscess
How does a Carbuncle occur?
Bacterial infections such as staph. Aureus or Gram Negative Bacilli spread to kidneys via blood or the ascending route from bladder.
Abscess results in flank pain, Fever and chills
What are the sonographic findings of a renal abscess?
Echogenic Renal mass Thick wall Irregular margins Reverberation or shadow artifact from gas-producing organisms Septations Possible acoustic enhancement
What is Xanthogranulomatous Pyelonephritis?
Due to chronic infection and obstruction of the uretero-pelvic junction from a staghorn calculus (blocking renal pelvis)
What will you find with Xanthogranulomatous pyelonephritis?
Renal enlargement Parenchymal abcess Staghorn calculus Papillary necrosis Possible hydronephrosis
What is Pyonephrosis?
Purple to material in the collecting system
Associated with renal obstruction
Percutaneous or surgical drainage is required
Echogenic debris in a dilated renal collecting system is seen on ultrasound
Etiology of Acute and Chronic Glomerulonephritis?
An antigen-antibody inflammatory response (autoimmune reaction) in the glomerulus, secondary to streptococcal infection
Leads to increased peritubular capillary permeability and cell proliferation resulting in leakage of proteins and RBC into the filtrate (ends up in tubules which congest area and slow down filtration process
Decreases GFR
Fluid and waste retention occurs, leading to ARF if prolonged
Chronic conditions can lead to CRF
What is the clinical presentation of Glomerulonephritis?
Flank pain
Hematuria
Edema (beginning at face)
HTN leading to headache, nausea, fatigue and stroke
What are the lab findings of Glomerulonephritis?
Increased creatinine
Increased BUN
Azotemia (abnormally high levels of nitrogen-containing compounds in the blood such as urea, creatinine)
RBC in urine
What are the sonographic findings of Glomerulonephritis?
Enlarged Echogenic kidney
Cortex will have equal echogenicity to sinus followed by increased cortical echogenicity
Post treatment of primary streptococcal infection will return the kidney’s size and echogenicity back to normal
What causes ARF?
Prinmary cause is Acute Tubular Necrosis (ATN) Decreased GFR Acute Glomerulonephritis Prolonged circulatory shock or trauma Septicemia Burns Interstitial nephritis Urinary tract obstruction Bilat renal artery occlusion or DVT Heart failure and Hypotension Tumors
What are the 2 phases of ARF?
Oliguria:
Decreased urine output
Tissue breakdown
Diuretic phase:
Few days to 6 weeks after onset
Increased urine output
Indicates nephron recovery
What are the clinical findings of ARF?
Oliguria Hypertension Muscle fatigue GI bleed Infections
What are the sonographic findings of ARF?
May be normal in early stages
Kidneys may also enlarge bilat
Homogenous echogenic pattern
Increased RI with hypoperfusion
What is the etiology of CRF?
Decrease in GFR Hypotension Diseases such as: AGN (acute glomerulonephritis) CPN (chronic pyelonephritis) Renal vascular disease Diabetes Toxins Polycystic disease
Clinical presentation of CRF
Early stage: Polyuria Nausea HTN Increased BUN & Creatinine Later stage: Oliguria Dry skin Impotence Encephalopathy CHF
What is the sonographic appearance of CRF?
Small, shrunken, echogenic kidney which is definitive of end stage renal failure
Kidney measures < 8 cm in length
Cortical thinning < 1 cm
What is Mycetoma?
Fungal ball
Candidiasis is another name
Most common renal fungal disease as a result from hematogenous seeding or ascend from bladder
Usually seen in immune suppressed patients such as AIDS
fungal balls appear as hyperechoic, non shadowing masses
When performing renal biopsy where should the needle be directed?
Lateral aspect of lower pole
10 degree cephalad angulation
What is the RI used for and what is its formula?
Used to evaluate renal transplants, access suspected hydronephrosis, medical renal disease and suspected renal neoplasm
RI= PSV-EDV/PSV
Where is a simple renal cyst found?
Commonly encountered in patients over 40 years old Found in 50% of patients over 50 Origin is usually unknown Serous fluid filled Usually solitary
What are the sonographic findings of a simple cyst?
Normal characteristics of a simple cyst
Range in size
98% accuracy with ultrasound
Mural growth may indicate malignancy
What types of simple cysts are there?
Cortical/single Cortical/multiple Pyelogenic cyst Parapelvic Peripelvic
Where does a pyelogenic cyst arise from?
Renal pelvis, infundibulum or calyces (calyceal diverticulum)
Show appearance of a simple cyst in ultrasound
What is a parapelvic cyst?
Cysts that bulge into the central sinus of the kidney which may cause symptoms and can be mistaken for hydronephrosis
What is a Peripelvic cyst?
Lymphatic cysts in the central sinus. Identical ultrasound appearance of parapelvic cysts
Note on renal cysts
Cortical cysts: originate from uriniferous tubules
Pyelogenic cysts: calyceal diverticula
Parapelvic cysts: parenchymal cysts
Peripelvic cysts: lymphatic cysts
Are hemorrhagic cysts associated with neoplasm?
Yes 31%
They can also be associated with trauma
Clinical symptoms of hemorrhagic cyst
Abdominal pain
Back and flank pain
Hematuria
What is MOC (Milk of Calcium)
Low grade inflammation and partial or complete blockage of a calyceal diverticulum
Quite common and represents calcium carbonate crystals
Sonographic appearance of MOC
Anechoic area near calyx
Echogenic mobile foci or gravity dependent wall
Acoustic shadowing
What is Medullary Sponge Kidney?
Congenital autosomal recessive defect Common/innocuous Localized to medullary collecting ducts Dysplastic cystic dilation of pyramids Bilateral, multiple cystic dilation Occurs in adults
What are complications of Medullary Sponge Kidney?
Calcifications in dilated cysts
Infection
Urinary calculi
Sonographic appearance of Medullary Sponge Kidney
Hyperechoic medullary pyramids bilaterally
Ectastatic collecting tubules
No shadowing
Acquired cystic disease
Patients on chronic hemodialysis develop bilat renal cysts
Hemorrhage often occurs into acquired cysts, resulting in pain, Hematuria and echogenic collections of cysts
Higher incidence of renal cell carcinoma
What is Tuberous Sclerosis?
Multi-systemic disorder associated with renal cyst formation and multiple angiomyolipomas (sebaceous cysts)
Patients present clinically with mental retardation, seizure and cutaneous lesions
Autosomal Dominant Polycystic Kidney Disease (ADPKD)
Cause is unknown Inherited Autosomal Dominant defect Potter III disease Latent until 3-4th decade Bilat disease Cystic origin: convulated tubules, bowman's capsule Incidence: 1-1000-2000 Leads to renal failure and requires transplant
Clinical findings of ADPKD
Flank pain
Back pain
HTN
Hematuria
Lab findings of ADPKD
Increased BUN
Increased creatinine
Hematuria
Proteinuria
Complications of ADPKD
Destruction of residual tissue
Advanced stages lead to renal failure and HTN
Associated with Berry’s Aneurysm: cerebral arterial/circle of Willis
What is the treatment for ADPKD?
Transplant
Autosomal Recessive Polycystic Kidney Disease (ARPKD)
Unknown cause
Theory states dilation of collecting tubules due to hyperplasia of interstitial portions
Inherited Autosomal Recessive defect
Potter I
Common in infants
Bilateral kidney involvement
Associated with renal dysfunction and hepatic fibrosis
Clinical findings of ARPKD
Oligohydramnios in utero
Cannot produce urine due to a,punt of cysts
Ultrasound appearance of ARPKD
BEEK: Bilateral, Echogenic, Enlarged Kidneys
Absence of renal parenchyma
Abscess of renal sinus
Multicystic Dysplastic Kidney
Cause by atresia of uretero-pelvic junction during fetal development
Most common cause of abdominal mass in newborn
It can be unilateral or bilat
Bilateral case can be fatal within 24 hrs of delivery
Potter II
Clinical findings of MDK
Oliguria
Anuria if bilat
Sonographic appearance of MDK
Cysts of varying shapes and size
Absence of communication between cysts
Absence of renal sinus and parenchyma
Renal architecture is gone
Renal Adenoma etiology
Most prevalent benign renal tumor From tubular epithelium Can only be distinguished from malignancy by histology Treated as malignant 3:1 ratio male over female Occurs usually in 6-7th decade
Clinical presentation of Renal Adenoma
Painless Hematuria
Ultrasound appearance of renal Adenoma
Similar to RCC Variable echogenicity Highly vascular May have internal echoes 1 cm in size mostly Rarely >3 cm
Angiomyolipomas (Renal Hematoma)
Fat, blood vessels and smooth muscle
Cortical lesions
More common in women
40-60 years old
Clinical findings of angiomyolipomas
May be asymptomatic
May have flank pain
Hematuria
HTN
Sonographic appearance of angiomyolipomas
Echogenicity is greater than or equal to renal sinus fat
Solitary
Posterior displacement of structures behind these masses may be seen as a result of the slower acoustic velocity in these fatty Tumors (propagation speed artifact)
Multiple associated with tubular sclerosis
Other names for Renal Cell Carcinoma
Hypernephroma
Etiology of RCC
Most common solid renal mass in adult 80-85% of adult renal tumor Unilateral Most common in men and African American 5-7th decade
Clinical findings of RCC
Pain
Hematuria
Palpable mass
Sonographic appearance of RCC
Unilateral, encapsulated solid mass
Hyperechoic in cortex relative to adjacent normal tissue
Multilocular cyst and hemorrhagic components may be present due to necrosis and hemorrhage
Calcifications are common
METS to liver, lymph nodes, adrenals and contralateral kidney
Stages of RCC
1: inside kidney
2: outside of kidney
3: goes to IVC
4: goes to lymph nodes and other organs
What is the treatment for RCC?
Nephrectomy
Associated findings with RCC
Von Hipple-Lindau syndrome Acquired cystic kidney disease ADPKD Tuberous Sclerosis Other syndromes associated with multiple cysts in kidneys
When RCC suspected, what other areas should be investigated?
Ipsilateral renal vein IVC Contralateral kidney and renal vein Retroperitoneum Liver for METS
Transitional Cell Carcinoma
Over 90% of TCC malignancies involve the renal pelvis and ureter
Majority of TCC arises in the bladder
Avg age diagnosis 61 yrs old
Clinical findings of TCC
Painless Hematuria
Hydronephrosis
Central filling defect on excretory urogram
Sonographic findings of TCC
Irregular hypoechoic mass in the renal sinus
Usually too small for US detection
Clot or fungal ball pattern
Hypoechoic to isoechoic collecting system mass
Secondary calyectasis
Multiple and bilat
Are papillomas bening but have high risk of developing to to TCC?
Yes
Renal lymphoma
Non-Hodgkin lymphoma is the most common type
Bilat enlarged hypoechoic renal masses
What is Wilm’s tumor?
Nephroblastoma Most common tumor in babies Malignant Arising from immature renal cells Less than 3 years old Large asymptomatic mass Mets is common to lungs, liver, bones, lymph nodes, adrenals and retroperitoneum IVC and renal veins should be evaluated for tumor extension Must be differentiated from adrenal neuroblastomas
Other names for kidney stones
Nephrolithiasis
Urolithiasis
Calculi
What causes nephrolithiasis?
Hot climates that promote dehydration, leading to concentrated urine and increases isolated precipitates of dissolved salts such as calcium oxylate, calcium phosphate
Risk factors for urolithiasis
Hereditary Renal dysfunction Bacteria Calyceal scarring Calyceal obstruction of collecting system Urine stasis
Clinical features of renal stones
Hematuria Oliguria Renal colic Nausea Vomiting Fever Pyuria Anuria Abdominal distention
Sonographic appearance of renal calculi
Echogenic foci
Posterior acoustic shadowing
Possible hydronephrosis
Hydroureter
What is nephrocalcinosis?
Calcifications of the kidney
What kind of nephrocalcinosis are there?
Cortical nephrocalcinosis and
Medullary nephrocalcinosis
Cortical Nephrocalcinosis Predispositions?
Hyperparathyroidism Vitamin D intoxication Chronic glomerulonephritis AIDS Malignancies Acute cortical necrosis
What is pelvocaliectasis?
Non-obstructive dilation of the collecting system
Where should RI be?
0.7
Grades of hydronephrosis
Grade 1 Mild hydro Dilated renal pelvis Grade 2 Moderate hydro Dilated calyces Grade 3 Severe hydro Dilated pelvis, calyces and cortical thinning or loss of renal parenchyma
What causes ureteric obstruction?
Pregnancy Fibroids Bening prostatic hypertrophy BPH Tumors Mass effect
What is Ureteropelvic Junction (UPJ) obstruction?
Common congenital anomaly.
Associated with a contralateral multicystic Dysplastic kidney
Where is the most common site of renal obstruction in an adult?
Ureterovesicle junction (ureter/bladder junction)
What causes UVJ obstruction?
Renal calculi
Pelvic tumors
Trauma
Infection
