Kidney Study Guide

Renal arteries arise from abdominal aorta, — cm just below SMA

2-3

Right renal artery courses — to IVC and its — than Left renal artery

Posterior, longer

Renal vein courses — to renal artery

Anterior

Left renal vein courses — to SMA and anterior to aorta and its — than right renal vein

Posterior, longer

What is the normal range in size for a kidney

9-12cm, cortex thickness >1cm (AP)

The renal arteries normally exhibit a — Doppler spectral waveform pattern characterized by constant forward diastolic flow

low-resistance (RI < 0.7)

Normal: peak systolic renal artery velocity less than — cm/sec, renal–aortic velocity ratio (RAR) less than —

180, 3.5

The formula for the RI is

PSV-PDV/PSV

Is a narrowing(decrease) in the diameter of the renal arteries is called

Renal artery stenosis (RAS)

Stenosis can cause renal insufficiency by inducing renal parenchymal damage. T/F

True

Common cause of RAS in older adults is —. In younger female patients is — disease

Atherosclerosis, fibromuscular

The most common symptom of renal artery stenosis is

Sudden onset of hypertension

“String of beads/pearls” sign represents

Fibromuscular dysplasia (FMD) of the renal arteries

Diameter reduction of — % is considered clinically significant

50-60

Renin-angiotensin system (RAS) or renin-angiotensin-aldosterone system (RAAS)is

hormone system regulates blood pressure & water balance

The 2 criteria’s that RAS can be diagnosed are

1. Proximal/direct criteria- direct findings obtained within the renal artery from origin to the hilum 2. Distal /indirect criteria- flow changes observed segmental and arcuate arteries

US appearance of RAS includes

1. Small kidney less than 2cm (differences greater than 2 cm in length between the kidneys) 2. PSV (peak systolic velocity < 180-200cm/s 3. (RAR) >3.5 3 4. Aliasing at the site of the stenosis 5. Presence of turbulence 6. Presence of “tardus– parvus” 7. RI >0.7 8- fibromuscular dysplasia (FMD)- “String of beads/pearls” sign of the arteries

The treatment of RAS is

Renal artery stent

A renal infarction is

When part of the tissue undergoes necrosis(death) after cessation of the blood supply due to vessel blockage by thrombosis or tumor

The ss (sign & symptom) for renal infarction includes

Sudden onset of abdominal or flank pain

The us appearance of acute and chronic renal infarction includes

Acute: 1. A wedge-shaped hypoechoic 2. absence of perfusion(flow) on color - and power-Doppler examination Chronic: 1. Echogenic 2. absence of perfusion on color- and power-Doppler examination

— is a kidney disorder involving damage to the renal tubule cells, resulting in acute kidney failure

Acute tubular necrosis (ATN)

Acute tubular necrosis (ATN) is caused by

Ischemia of the kidneys (lack of oxygen to the tissues)

US of acute ATN includes

1. Enlarged kidneys 2. Hyperechoic pyramids which can revert to normal appearance 3. Hyperechoic cortex 4. Increase resistive index (0.7)

Abnormal communication between renal artery and vein is called

Arteriovenous fistulas

Arteriovenous fistulas are commonly caused

Due to renal biopsies

Us appearance of AVFs include

1. Cystic area (2D imaging) 2. Increased flow velocities 3. Pulsatile flow 4. Decreased resistive indexes 5. Arterialization of the vein

Pseudoaneurysm (PSA) of the renal arteries is — and its usually caused by

PAS arises when there is a hematoma that forms as the result of a leaking hole in an artery, most likely secondary to the disruption of one or more layers of the vessels wall Commonly caused by trauma or biopsies(procedure) and its associated with AVFs

US appearance of pseudoaneurysm (PSA) includes

1. Anechoic outpouching on the grayscale US 2. Bidirectional swirling flow noted on color "yin _ yang" sign 3. To-and-from Doppler/ biphasic/ Bidirectional/ signal in the neck

Blood clot within the renal vein is called

Renal vein thrombosis

Renal vein thrombosis is cause by

Hypercoagulability disorders, renal tumor, trauma, renal infections (pyelonephritis, glomerulonephritis), or be seen following a renal transplant.

The ss (sign & symptom) for renal vein thrombosis includes

Flank pain and hematuria

Us appearance for acute RVT includes

1. Enlarged hypoechoic kidney 2. Enlarged renal vein with echogenic lumen 3. No flow (Doppler signals) within the renal vein 4. Increased renal artery resistance, reversed flow in renal arteries biphasic phasic waveform

Us appearance for chronic RVT includes

With chronic case the kidneys will be small and echogenic

— Results most commonly from the compression of the left renal vein between the abdominal aorta (AA) and superior mesenteric artery (SMA)

Renal vein entrapment syndrome/nutcracker syndrome

Clinical manifestations of nutcracker syndrome are

left flank pain, pelvic pain, hematuria and gonadal varices

Us appearance of nutcracker syndrome

Enlarged LRV, testicular varicocele

Renal parenchymal disease affects which parts of the kidney and the us appearance is

Cortex and medulla, us RI>0.7

Any tissue transplanted from one human to another human is called

Allograft

A renal transplant is a treatment for

Chronic renal failure or end stage disease

— is the most common cause of kidney transplant

Diabetes mellitus

Most transplants are placed extraperitoneally in the —

iliac fossa(right(common) or left)

Commonly RA is anastomosed(connected) to — and RV is anastomosed to —

EIA (external iliac artery), EIV

Native kidney is usually left in place. T/F

True

Baseline obtained within — hours postop

The donor kidney is usually taken from the — side because the — vein is longer than the right renal vein AND the doctor doesn’t have to worry about the liver

Left, left renal

Transplanted kidney should look like a normal kidney in shape and echotexture. T/F

True

Normal Resistive index (RI) should be < 0. —

0.7

The renal vein should demonstrate normal — flow away from the kidney

Continuous

As a sonographer, the renal transplant should be evaluated

1. Size 2. Echotexture 3. Vasculature - Doppler—flow 4. Hydronephrosis 5. Fluid collections

As early as — hours after surgery, a baseline us examination is performed. First follow-up scan at 1-2 week

48

Because of its superficial location, use -----------frequency transducer 5 - 7 MHz curvilinear

High

The vessels that should be includes for patency(openness) of the blood vessels, and to calculate the RI index are

1. Main renal artery 2. Segmental arteries 3. Interlobar arteries 4. Arcuate arteries 5. Interlobular

The sonographer should document the RI for the renal vein. T/F

False

What are the land marks for renal branches

1.Renal arteries at the level of the hilum 2. segmental arteries at the level of renal pelvis 3. interlobar arteries at the level of renal pyramids 4. arcuate arteries, runs along the base of the medullary pyramids or parallel to the cortex - are used to assess parenchymal resistance 5. interlobar arteries runs perpindicular to the renal capsule

Complications of a renal transplant includes

1. Rejection 2. Obstruction- hydronephrosis 3. Renal artery stenosis 4. Renal vein thrombosis 5. Arteriovenous fistula (AVF) 6. Pseudoaneurysm 7. Acute Tubular Necrosis (ATN) 8. Abscess 9. Fluid collection

Transplant Rejection results from an attack by the

Immune system on the transplanted organ

— are used to treat rejection

Immunosuppressant drugs (cyclosporine & tacrolimus)

Rejection is suspected

1.With sudden cessation of urine output (anuria) 2. decreased urine output (oliguria) 3. increase in serum creatinine, protein, or lymphocytes in urine 4. hypertension

— used for definitive diagnosis for transplant rejection

Biopsy

Acute rejection by us includes

1. Increased renal size 2. Prominent hypoechoic medullary pyramids 3. Thickening of renal pelvis 4. Increased resistive index (RI) >0.7may indicate rejection) 5. Renal vein thrombosis -no flow can be seen in rejection

Acute Tubular Necrosis is caused by —

Ischemia

ATN is the most common cause of acute renal failure in an allograft. T/F

True

US appearance of ATN include

1. Increased resistivity (>0.70) & pulsatility 2. Increased cortical echogenicity seen

Most common vascular complication after kidney transplant is

Renal artery stenosis

The most common ss for RAS is

Patients present with severe uncontrolled hypertension

Causes of RAS in transplant cases include

1. Postsurgical scarring or dissection 2. Intimal hyperplasia 3. Progressive atherosclerosis 4. Rejection

Sonographic findings of RAS includes

1. Small kidney size. Differences greater than 2 cm in length between the kidneys is suggestive of renal artery occlusion 2. Peak systolic velocity >180-200 cm/sec AND renal-aortic ratio greater than 3.5, poststenotic turbulence is present. Turbulence exist distal to the narrowing 3. Absence of early systolic peak,’’tardus & parvus’’ waveform pattern distally 4. RI >0.7

Venous or arterial thrombosis suspected — in region of transplant

with sudden anuria or acute onset of pain

Risk factors include RVT

1. Hypercoagulable states 2. Hypotension 3. Intraoperative trauma 4. Mismatch of vessel size vascular kinking

Sonographic findings of renal artery thrombosis include

1. Intraluminal echoes 2. Absence of arterial flow on color, power, or spectral Doppler of intrarenal or main renal arteries

Sonographic findings of acute renal vein thrombosis include

1. Enlargement of kidney 2. Decreased renal cortical echogenicity 3. Enlarged main renal vein; with low level echoes4. Absence of flow on color, power, or spectral 5. Doppler- Presence of reversed flow in renal arteries Biphasic phasic waveform

Post biopsy vascular complications abnormalities include

1. Arteriovenous fistula (AVF) 2. Pseudoaneurysm (PSA)

What is an abnormal connection or anastomosis between an artery and a vein

AV fistula

In case of AV fistula — & — can be observed

Color aliasing, bruit

A bruit is

A rumbling sound that you can hear

A thrill is

a rumbling sensation that you can feel

A bruit and a thrill is highly suspicious for

AVFs

US appearance of AVFs

1.Color Doppler imaging of AVFs will often demonstrate a bruit artifact (color bruit artifact) and/or a thrill. A bruit and a thrill are highly suspicious for AVFs 2. Pulsatile flow 3. Decreased resistive indexes, higher velocity flow 4. Arterialization of the vein (abnormal arterial pulsatility in the vein)

Obstruction of the kidney (calyces) due to urine failing to properly drain from the kidney to the bladder is called

Hydronephrosis

Mild dilatation/mild pelviectasis is normal post transplantation. T/F

True

Patency of the ureters can be proven sonographically by demonstrating — with color Doppler in the bladder

Ureteral jets

US appearance of hydronephrosis includes

1. Dilatation of the calyces 2. Increase RI>0.7

US appearance of renal transplant infection/abscess includes

1. Hypoechoic irregular mass 2. Debris or low-level echoes within a dilated collecting system suggests pyonephrosis 3. Shadowing or reverberation artifacts- if it is caused by gas forming bacteria

— is the most common transplant fluid collection that occurs with surgical disruption of the lymphatic chain. Usually appear 4-8 weeks posttransplant

Lymphocele

Urinoma is defined as a

leaked urine

— lab value indicates hematoma and — lab value indicates perinephric abscess post-transplant

Decrease hematocrit value, increase WBCC

Moderate to large fluid collections post-transplant are generally NOT normal, requiring aspiration and/or medication. T/F

True

By us fluid collections appear as

Cystic structures with or without echoes, with or without septations

Ultrasound appearance of chronic renal transplants rejection includes

1. Increase of echogenicity throughout kidney 2. Kidney decreased in size (<9cm), thin echogenic cortex (<1cm) 3. Non-differentiation between renal sinus and parenchyma 4. Increased RI