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Precious Stones: Gems of the urogenital system

Nordic Forum 2017, Helsinki, Finland

Ken F Linnau MD, MS

Emergency Radiology

kingstonegems.com

59 year old woman

• Intermittent right flank pain

• Pain radiates into the right groin

• Hematuria

• No abdominal tenderness on exam

What does she have?

– Diagnosis and differential

What needs to be done?

– Medical treatment or surgical intervention

Outline - Nephrolithiasis

• Rationale approach to imaging diagnosis

• CT KUB vs US

• Differential considerations

• Imaging technique

• Low dose scan

• Positioning

• Unusual urolithiasis

• Indinavir stone

• Staghorn calculi

• XGP

• Bladder stones

• Dual Energy CT and nephrolithiasis

59 year old woman

• Intermittent right flank pain

• Pain radiates into the right groin

• Hematuria

• No abdominal tenderness on exam

What does she have?

– Diagnosis and differential

59 yof rt flank pain and hematuria

CT findings of nephrolithiasis

• Dens calculus in the course of the urinary collection

system

Indirect secondary signs:

• Dilatation of the upstream collecting system • Increases with duration of pain

• Perinephric fat stranding

• Includes the peripelvic renal fat

35 yof RLQ and rt flank pain

US findings of nephrolithiasis

• Echogenic calculus in the course of the urinary

collection system

• Posterior acoustic shadowing

Indirect secondary signs:

• Dilatation of the upstream collecting system • Increases with duration of pain

CT or US for suspected nephrolithiasis?

• Non-contrast helical CT and Ultrasonography

• Both are appropriate initial imaging modalities.

• Missed diagnoses resulting in complications are

equivalent.

• Serious adverse events are similar.

• Return visits to ED are similar.

• Length of stay in ED is longer when US is done by

radiologist.

Smith-Bindman R, et al. NEJM (2014): 371;12: 1100

CT vs US

CT US

Sensitivity 88 54 vs 57

High specificity and positive exam confirms diagnosis

41% needed CT after US

Radiation

70% more dose at 6 months

Alternate diagnosis in 33%

Smith-Bindman R, et al. NEJM (2014): 371;12: 1100

42 yof with right sided abdominal pain for several days.

Now localizing to RLQ, N/V, WBC 13 tsd, UA: ++ RBC

DDx for nephrolithiasis

• Appendicitis, intestinal obstruction, diverticulitis:

• No hematuria, usually abdominal tenderness

• Ovarian torsion, ruptured cyst, dysmenorrhea

• Billiary colic or cholecystitis

• No hematuria

• Less common:

• Aortic aneurysm

• Intestinal ischemia

• Ectopic pregnancy

• Herpes zoster

Hematuria useful disciminator

No hematuria in 10-30% of nephrolithiasis,

especially when onset of pain more distant

43 yom colicy LLQ pain, r/o diverticulitis

Treatment of urolithiasis

• Pain control: NSAIDs

• If urosepsis: emergent decompression

• Ureteral stent or nephrostomy

• Stone < 10 mm: usually passes

• Treat symptoms

• Stone > 10 mm: urologic evaluation

• Extracorporeal Shock Wave Lithotripsy (ESWL)

• Nephrolithotomy

43 yom colicy LLQ pain, r/o diverticulitis

Pelvic phlebolith

31 yom rt flank pain

CT technique

• Low dose technique

• Similar sensitivity and specificity for larger stones

• Less reliable for stones < 2 mm

• Less reliable in obese patients BMI > 30

• Consider prone scanning position

• Allows detection of passed stones (dependent location)

53 yom rt flank pain, HIV+, on HAART

59 yof lt flank pain


https://www.pinterest.com/monfakwei/antlers


CT KUB from 3 months earlier

Staghorn calculi

• Struvite (Mg ammonium phosphate)

or Ca++ carbonate apatite stones

• Branched stones that fill part or entire renal pelvis

• “Infection stones”

• Strong association with UTIs

• Urea splitting organisms (Proteus, Klebsiella)

• Can grow rapidly

• Deterioration of kidney function

• End-stage renal disease

• Urosepsis

• Surgical treatment often necessary

• Shock wave lithotripsy

• Percutaneous nephrolithotomy

https://www.pinterest.com/monfakwei/antlers

87 yom s/p fall

PV

10 min delayed

Xanthogranulomatous pyelonephritis (XGP, XPN)

• Renal tissue is replaced: chronic inflammation

• Dilated calices surrounded by

• Xanthomatous tissue (“yellow”)

• Necrosis, inflammatory cells: lipid-laden macrophages

• Giant cells and cholesterol clefts

• Unilateral

• Renal stones, often staghorn stones

• Infrequent association with renal cancer

• Peri-renal extension and fistulation

• Nephrectomy

60 yom CP, fall during wheelchair transfer

66 yom SCI patient annual surveillance

Bladder stones

• Urinary calculus in bladder

• Bladder outlet obstruction (e.g. BPH)

• Foreign body (e.g. urethral catheter)

• Infections with urea-splitting bacteria

• Neurogenic bladder


Dual Energy CT image

Dual Energy (DE) CT

• Two x-ray sources and 2 data acquisition systems mounted on same x-ray gantry

• Each x-ray source has independent high voltage generator

• Allows for independent control of both potential and current

– E.g.80/ 100 kV & 140 kV

• Simultaneous low & high energy images can be reconstructed

Remy-Jardin et al. Radiol Clin North Am. 2010 Jan;48(1):193-205. Courtesy S Nicolaou, UBC, Canada

• Xrays: electromagnetic radiation of different wavelenghths: spectrum

• X-ray spectrum differs by kV

• Tin pre-filtration for 140 kV

• Spectral separation allows characterization of materials

DE CT exploits X-ray spectrum

S1: 80 kV x 104

15

10

5

0 50 100 150

80 kV

140 kV

photon energy (keV)

0.4 mm Sn

+ SPS

140 kV + SPS

S2: 140 kV

Courtesy S Nicolaou, UBC, Canada and Siemens

Principle of Dual Energy CT

Courtesy S Nicolaou, UBC, Canada

Principle of DE CT

Courtesy S Nicolaou, UBC, Canada and Siemens

Johnson T et al. Eur Radiol. 2007; 17:1510-7.

Material Characterization Materials can be differentiated by applying two X-ray spectra and analyzing attenuation differences. Technique works well for compounds with high atomic numbers taking advantage of the photoelectric effect ~Z3


• Bone • Iodine • Uroliths

Image Based Methods Modified 2-material decomposition: Characterization of kidney stones

• Calcified stones are BLUE (heavy ions)

Uric acid stones are RED (Nitrogen, Oxygen containing)

HU at 140 kV

HU at 80 kV

high Z

low Z



Calcified stone, mixed composition


Uric acid stone

DE CT stone characterization

• Uric acid stones respond well to medical therapy • DE ratio around 1.0

• Cysteine stones are resistant to ESWL

• Calcium stones are most common, different

types

• Calcium oxalate monohydrate least susceptible to

ESWL

• DE ratio < 1.4

• Other calcium containing stones more fragile: ESWL

DE CT can be helpful to in treatment decision

making

Summary

• Hematuria?

• Non-contrast CT and sonography are equivalent first

tests

• Use low dose technique and prone positon for CT

• Stone size and location is important for treatment

• DE CT for stone composition

Thank you. [email protected]

kingstonegems.com

References

• Ultrasonography versus computed

tomography for suspected nephrolithiasis.

Smith-Bindman R, Aubin C, Bailitz J, Bengiamin RN, Camargo CA Jr,

Corbo J, Dean AJ, Goldstein RB, Griffey RT, Jay GD, Kang TL, Kriesel

DR, Ma OJ, Mallin M, Manson W, Melnikow J, Miglioretti DL, Miller SK,

Mills LD, Miner JR, Moghadassi M, Noble VE, Press GM, Stoller ML,

Valencia VE, Wang J, Wang RC, Cummings SR. N Engl J Med. 2014 Sep

18;371(12):1100-10. doi: 10.1056/NEJMoa1404446. PMID: 25229916

• In vivo characterization of urinary calculi on dual-energy CT: going a step

ahead with sub-differentiation of calcium stones. Acharya S1, Goyal

A1, Bhalla AS1, Sharma R2, Seth A3, Gupta AK1. Acta

Radiol. 2015 Jul;56(7):881-9. doi: 10.1177/0284185114538251. Epub

2014 Jun 17. PMID: 24938664

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