Notes #10: Renal Infections / Inflammations / Calcifications / Obstruction

Renal Failure:

also known as uremia

toxic condition associated with renal insufficiency

symptoms secondary to retention of nitrogenous waste products

Symptoms:

High Blood Pressure

Nausea, vomiting

GI ulcers, inflammations d/t increase serum ammonia

Cardiac arrhythmias d/t potassium, Calcium imbalances

Edema and fluid retention

Anemia d/t decrease in erythropoietin

Urine flow changes

Dizziness

Coma, convulsions

Nephrotic Syndrome (not a single entity but a stage in chronic renal disease marked by proteinuria, decreased plasma protein, rise in serum lipids, edema)

Elevated BUN, creatinine, ammonia

Acute renal failure:

sudden impairment

symptoms develop within hours or a few days

usually secondary to radiation, chemical, or toxin exposure, to sudden decrease in blood volume, or to acute infection

Chronic renal failure:

result of chronic renal disease
develops over many years

Major Classifications of Renal Disease:

Type I Renal Disease:

any of a large group of renal medical diseases that originate with injury or infection of the glomeruli and lead to renal failure.

Sonographic Characteristics:

Initially edema and enlargement of the kidney

Progressive increase in echogenicity of the cortex

Progressive decrease in size

Increased definition of cortico- medullary junction

Pyramids may appear enlarged as cortex shrinks

Echogenicity of cortex and size of the kidney correspond to severity of disease, prognosis of kidney

Grade 1: Renal cortex echogenicity = liver

Grade 2: Renal cortex echogenicity > liver

Grade 3: Renal cortex echogenicity = sinus echoes

Small (length <10cm) echogenic kidneys = poor prognosis

Normal sized echogenic kidneys = better prognosis

Type II Renal Disease:

Renal Inflammations and miscellaneous renal diseases that originate in the pelvis or medulla. These diseases have multiple causative agents usually coming from the ureter and leading to pyelonephritis. Type II disease may eventually cause renal failure by generalized progression into the cortex. Type II diseases are, however, more variable in appearance and outcome than are Type I.

Sonographic Appearance:

Variable in appearance

Show disruption of pyramid - medullary echoes

Distort normal anatomy and eliminate corticomedullary boundary definition

Type I Renal Diseases:

Prerenal Origin of Renal Failure:

diminished blood flow to kidneys can lead to interstitial damage

Congestive Heart Failure

Decreased Blood Volume from hemorrhage or surgery

Renal Artery Stenosis

Metabolic vascular diseases such as Diabetes

Renal Vein Thrombosis (may be secondary to renal cellcarcinoma, retroperitoneal tumors, diabetes)

Sonographic Analysis:

Echogenic material within RV or RA

Normal Venous Pattern in RV may be absent

Vascular calcifications - shadowing in pelvic area

Glomerulonephritis:

Large group of diseases where the initial pathological involvement is the glomeruli located in the cortex of the kidney

Leads to proteinuria, hypertension, and other signs of renal failure.

Causative Agents:

Infectious agents carried through the blood system

Strep, Malaria, Syphilis
Toxins such as snake venom, drugs, metals, fumes

Pressure damage due to PKD, severe hydronephrosis

Autoimmune Inflammation due to lupus nephritis,

Goodpasture's Syndrome - antibodies to lung, kidney

Acute cortical necrosis

Ischemic necrosis d/t shock, hemorrhage, burns,

Intrarenal arterial stenosis of venous thrombosis

toxemia of pregnancy, severe dehydration

May be localized or generalized

Leads to increased cortical echogenicity in the area due to necrosis, calcific deposits and fibrosis

Amyloidosis:

Deposition of abnormal protein fibers in amounts sufficient to impair renal function

Associated with acute and chronic infections, and immunologic disorders such as rheumatoid arthritis, lupus, certain tumors (especially myeloma), and aging

Deposits occur in spleen, liver, kidneys, lymph nodes, heart, lungs, GI tract, throughout body

Leads to rubbery consistency - renal failure

Type II Renal Disease:

Acute Tubular Necrosis:

Results from tubular epithelial destruction

Toxins common cause

Sonographically normal kidneys

Symptoms of acute renal failure with nl kidneys - likely ATN

Particularly a problem with renal transplants from cadaever

Myoglobinuria:

Similar to ATN, but secondary to alcohol or drug abuse

In some cases the pyramids may be prominent or swollen

Renal Papillary Necrosis:

Associated with diabetes, severe infantile diarrhea, obstructive uropathy, sickle cell anemia, acute or chronic pyelonephritis, chronic alcoholism

Presents with small cystic areas or increased echogenicity in the medulla

Xanthogranulomatous Pyelonephritis:

Inflammatory disease secondary to long-standing obstruction

Xanthro = yellow lipid deposits

Enlarged kidneys with stones present in majority of cases

Staghorn calculi-large stone center

Single or multiple renal masses present, usually hypoechoic or anechoic

Abscesses filled with yellow lipid usually peripelvic

Debris filled dilated calyces

May be segmental associated with obstruction of single calyces

Distortion of normal anatomy

Bacterial Interstitial Nephritis (Pyelonephritis):

May result from infection, obstruction, urinary stasis

Kidney may appear normal initially

Decreased echogenicity throughout kidney and enlargement

Obliteration of corticomedullary junction - sinus echoes also appear less echogenic, blend into parenchyma

Dilated calyces single or multiple

Focal Nephronia, and Abscesses may develop

Symptoms: Fever, chills and flank pain

Localized Infections

aka Focal Nephronia, aka Lobal Nephronia, aka Acute Focal Bacterial Nephritis

Localized Inflammatory Mass

Small ill-defined borders

Wedge shaped area of reduced echogenicity without liquidification

Abscess Formation

Liquidification, pus formation

Better border definition, liquid component

Irregular shape

Enhancement, Debris, fluid/debris levels

Increasing size of mass area

Carbuncle

Mature abscess

Thick-walled, discrete, complex, round shape, decreasing size

Emphysematous Infection

contain gas which cause stong echoes and shadowing

Infection may remain within the kidney of may break throught the renal capsule to the perirenal space where it tends to localize in fat posterior/lateral to the kidney near psoas muscle. May cause elevation of the kidney. Gerota's fascia usually prevents further spread.

Important to visualize renal capsule to determine if intrarenal or perirenal abscess.

Treatment:

Drainage of abscess under ultrasound or fluoroscopic guidance

Surgical removal of mature abscess

Nephrectomy in severe cases

Renal Tuberculosis:

Multiple abscesses with debris common

Associated with pulmonary Tb and AIDS

Strictures in calyces often lead to hydronephrosis

Ascites may develop

Fungus Balls:

Echogenic non-shadowing mass in the collecting system often associated with fever, chills, flank pain.

Occurs most usually in patients with lowered resistance, from diabetes, malignancy, chronic illness, or medication.
Differential diagnosis: blood clot, tumor, debris

Renal Sinus Lipomatosis:

Replacement lipomatosis in sinus

Kidney may be normal in size or enlarged with increased width of central echoes, thin renal parenchyma

Common in older patients

Sequelae to chronic stone or inflammation

Also a normal variant with obesity, aging

Renal Calcification and Obstruction:

Only 5% of renal failure is due to obstruction, but this is the easiest cause to treat. It is essential to screen all patients with symptoms of renal failure for obstruction so quick surgical intervention can be undertaken.

Obstructive Causes of Hydronephrosis:

1.Congenital atresia of urethra, kinking of ureter, mal-position of ureter

2.Foreign bodies, calculi (urate stones most common), sloughed papillae or blood clot.

3.Tumors
Benign Prostatic Hypertrophy, Prostate Carcinoma, Bladder tumors, Cervical Ca, Endometrial Ca

4.Inflammation (prostatitis, UTI, pyelonephritis)

5.Post operative trauma, retroperitoneal fibrosis

6.Gynecologic inflammations - endometriosis, TOA and resulting fibrosis

Non-obstructive causes of Hydronephrosis:

1.Spinal Cord Damage, Paralysis of Bladder

2.Normal pregnancy (mild and reversible hydronephrosis)

3. Reflux

4. Infection

5. Diuresis - esp. dehydrated patient undergoing rehydration

6. Distended Bladder

7. Extrarenal pelvis

8. Papillary necrosis

9. Calyceal diverticulum

10. Corrected obstruction


11. Neurogenic bladder post operative or due to chronic disease

Hydronephrosis generally unilateral and asymptomatic

Pyonephrosis is hydronephrosis with coexisting infection, debris/purulent material in fluid

Symptoms if present vary:

Oliguria if bilateral complete obstruction

Polyuria may develop in incomplete obstruction due to inability of tubules to concentrate

Change in size or force of urine stream

Severe colicky pain to vague flank pain

Amount of Fluid dependent on duration of obstruction and renal output - amount of residual cortex more important than amount of fluid.

Sonographic Appearance:

Mild Hydronephrosis:

Slight separation of pelvis or cystic appearance of calyces, infundibulum connection to pelvis separates from renal cyst.

Moderate Hydronephrosis:

All calyces enlarged, cauliflower shape

Severe Hydronephrosis:

Shape of calyces no longer discernible.

Kidney can reach up to 20 times normal size.

Thinning of cortex usually apparent.

Sites of Obstruction:

UPJ - ureteral pelvic junction
Most common site for obstruction

congenital strictures

calculi or foreign body obstruction

retroperitoneal tumor impingement

UVJ - ureteral vesicle junction

Obstruction most commonly due to extrinsic compression, ex. pelvic lymphoma, pelvic abscess, ovarian mass, or large abdominal mass

Right sided obstruction most common in women

Dilated ureters seen as tubular anechoic structures running from kidney to bladder or as circular anechoic areas posterior to the bladder on transverse view

Color flow of ureteral jets can confirm unilateral UVJ obstruction

Ultrasound may not locate site of obstruction in ureter

Bilateral Obstruction:

Least common site for obstruction
may be due to bladder outlet or urethral obstruction associated with bladder or prostate tumor or cervical carcinoma

spinal cord damage, paralysis of bladder, urethral motility problems, other non-obstructive causes

Lesions confused with Hydronephrosis "False Positives"

Central renal cysts

Multicystic Kidney

Sinus Lipomatosis

Peripelvic cysts

Sonolucent renal pyramids

Lumbar meningomyelocele

Pancreatic Pseudocysts

Sonolucent Masses (Lymphoma, Leukemia, other mets)

Aneurysm/Varices of Renal Vasculature in renal hilum

Associated with failure to recognize obstruction or hydronephrosis "False Negatives"

Staghorn calculi - shadowing obscures visualization

Numerous cysts with superimposed hydronephrosis

Acute renal disease - no output of urine so minimal dilation

Associated Pathology:

Urinoma "renal pseudocyst"

escape of urine, encapsulated by body
appears as an anechoic mass usually posterior to kidney between the renal capsule and Gerota's fascia.
Can lead to retroperitoneal fibrosis, perinephric abscess

Nephrolithiasis or renal calculi

Results from calcium salts in renal system

More frequent in males than females

Overall incidence 0.1% - 6% of the population

Can arise anywhere in urinary system, but most common in kidney

Causes: Hypercalcuria or hypercalcemia due to geographic location (water source), hyperparathyroidism, Vit D intoxication, malignancy, bone disease, dehydration, or Cushing's disease

Large single stones may be located in center of kidney with shadowing apparent (Staghorn calculi). These are named by their appearance on radiography.

Multiple smaller stones can be visualized by ultrasound in the pelvis or near the corticomedullary border

Diffuse nephrocalcinosis

Classic - small stones or deposits along the corticomedullary borders

Cortical Calcification

Deposits in parenchyma of the kidney
in severe form the entire cortex is strongly echogenic, may appear similar to severe Type I renal disease

May not shadow

CT can differentiate from renal disease

Medullary Calcification

Medullary pyramids become echogenic while the cortex retains normal echogenicity

May not shadow - microscopic aggregates cause scattering of beam, but no shadows

Primary Hyperoxaluria

Rare, metabolic disease - hereditary

Leads to death before adulthood

Presents with renal stones in childhood

Calcium oxalate deposits in cortex lead to renal failure

Hyperechoic cortex with pelvic stones

Calyceal Diverticuli

Cystic extension of calyces
Connected to system, but flow through area is slow predisposing to stone formation.

May appear as gravity dependent echogenic debris within a cystic structure or calcification within a cystic structure

May become filled with milk of calcium (gravity dpn. echogenic debris)