2. Introduction
• Pain resulting from urinary stones is the commonest cause of abdominal pain
requiring hospitalization during pregnancy
• incidence - 0.026% and 0.531%
• Unlike the rest of the population , the incidence of urolithiasis in pregnant women
did not increase when comparing 1991-2021.
• Symptomatic stones occur in 1 in 250 to 1 in 3000.
• 40% of premature births
• No difference in incidence - symptomatic stones during pregnancy compared to
nonpregnant women of childbearing age group
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3. • multiparous women seem to be affected more often than primipara by a ratio of
approximately 3:1
• Left and right side calculi occur with equal frequency
• ureteric stones occur approximately twice as often as renal calculi.
• 80%–90% of patients present in the second or third trimester of pregnancy, while
first trimester presentation is rare
• The diagnosis can be difficult in these patients as upto 28% of women are
misdiagnosed as appendicitis, diverticulitis or placental abruption
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4. Effects of Pregnancy on the Urinary Tract
• Physiological hydronephrosis - up to 90%
• starting at 6–10 weeks of gestation, and generally resolves within 4–6 weeks of parturition.
• HN is due to a combination of hormonal and mechanical effects.
• Progesterone causes decreased peristalsis and dilatation of the ureter above the pelvic brim.
• Although HN may be in part due to effects of progesterone , compression of the ureters by
gravid uterus is at least a contributory , if not primary factor
• right > left, due to compression from the engorged right ovarian vein and uterine
dextrorotation.
• Calyceal rupture mc on right than left.
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5. • The physiological dilatation may promote crystallization as a result of urinary
stasis.
• The increased renal pelvic pressure has been suggested to increase the likelihood
of stone movement and symptoms.
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7. • Absorptive hypercalciuria - placental formation of 1,25-dihydroxycholecalciferol which
increases intestinal calcium absorption and secondarily suppresses PTH.
• Resin et al demostrated that hypercalciuria of pregnancy is reversible physiological
condition
• filtered loads of antilithogenic substances like citrate, magnesium, and urinary
glycosaminoglycans are also increased.
• Hypercalciuria in alkaline urine favors the crystallization of calcium phosphate
(rather than calcium oxalate) stones (75%)
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8. • Despite increase in a number of stone-inducing analytes, pregnant women have
been shown to excrete increased amounts of inhibitors such as citrate, Mg and
glycoproteins
• Therefore the overall risk of stone formation has been reported to be similar in
gravid and nongravid women.
• The higher prevalence of calcium phosphate stone stones observed in in
pregnancy may suggest that changes in pH during pregnancy could contribute
for the same , although this remains speculative.
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9. Fetal Considerations - Radiation Exposure
• human body absorbs almost 90% of the exposed diagnostic radiation
• the radiation dose absorbed (amount of energy deposited in the tissue by
radiation) by a person is measured using the unit Rad or Gray (Gy).
• Biologic risk ( risk that a person will sustain health effects from an exposure to
radiation, dose equivalent and effective dose of) radiation exposure is measured
using the unit Rem or Sievert (Sv)
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10. • principal effects - teratogenesis, carcinogenesis, and mutagenesis
• The effects : nonstochastic or stochastic.
• Nonstochastic effects - cumulative with increasing dose and for which a threshold (< 50 mGy
are considered as safe) is believed to exist. Eg; malformation, growth retardation, and cataract
formation (teratogenic)
• Stochastic effects - probability of the effect gets worse with increasing dose and where there
appears to be no threshold. Eg; the risk of malignancy and genetic effects.
(Carcinogenesis- dose even < 10 mGy present a risk and mutagenesis - 500-1000 mGy doses are required)
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11. • acute exposure to radiation >0.5 Gy represents a major risk to the embryo
• The risk is critically dependent on - gestational age and the total amount of
radiation delivered
• Exposure to fetus: X ray KUB - 0.5 mGy , standard IVU - 3 mGy and a limited IVU -
2 mGy
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14. Clinical Presentation
• flank pain (MC), gross or microscopic hematuria, UTI, irritative LUTS, and
rarely with preeclampsia
• Incorrect diagnoses - appendicitis, diverticulitis, and placental abruption ( 28% cases)
• microscopic hematuria reported in up to 75% of cases and gross hematuria in up
to 15% of cases
• Bladder stones are reportedly rare during pregnancy (often missed on USG)
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16. Choice of Imaging Modalities
Ultrasound (US):
• Initial diagnostic test of choice
• difficult to differentiate the physiological dilatation of pregnancy from ureteric
obstruction
• miss up to 20% of patients with complete obstruction
• 34% sensitivity and 86% specificity for urolithiasis
• ureteric dilatation below the pelvic brim is highly suggestive of pathological distal
ureteric obstruction.
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17. • use of resistive index, presence or absence of ureteral jets, and measurement of
pelvic diameter has been conflicting.
• abnormally elevated RI was defined as ⩾0.70 and a significant ΔRI (interrenal
difference in RI) as ⩾0.08
• transvaginal US may help in elucidating the level of obstruction (distal)
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19. MR Urography (MRU)
• 1.5T is currently recommended
• Safety or efficacy of a 3 T MRI machine during pregnancy has not been assessed.
• Acoustic injury to the fetus during pregnancy appears to be more hypothetical
• MRI protocols for pregnant pts - rapid acquisition with relaxation enhancement
(RARE) (Sn-100%), fast spin-echo (FSE), and half-Fourier acquisition single-shot
turbo spinecho (HASTE)
• reserved for special cases when US fails to provide a diagnosis
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20. • gadolinium contrast- potential fetal toxic effects in animal studies, need for - risk
benefit analysis.
• Stones are seen as filling defects/ signal void.
• Identifies level of obstruction
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22. Intravenous Urogram (IVU)
• difficulty in differentiating delayed excretion of the contrast associated with
physiological dilation from that associated with obstruction due to calculus
• enlarged uterus and fetal skeleton may obscure small stones.
• Depression of fetal thyroid function is a potential side effect ( free iodide )
• exposure to contrast media should be avoided.
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23. Computed Tomography (CT)
• radiation dose from CT scan of the pelvis could potentially double the risk of
developing childhood cancer
• low-dose CT (LDCT) - higher PPV (95.8%), improved diagnostic accuracy
• avoid negative interventions such as ureteroscopy .
• low-dose CT can be defined as <3.5 mSv, and ultra-low dose as <1.9 mSv
• safe in pregnancy from the non-stochastic teratogenic standpoint, but not stochastic
effects including delayed hematologic malignancy.
• judicious use is currently recommended in pregnant women as a last-line option
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24. Radionuclide Renography
• exposure of the fetus to radioisotope radiation emitted from adjacent maternal
organs and from any radioactivity transferred across the placenta
• Renography delivers about 10% of the radiation dose of an IVU.
• 99mTc - absorbed dose - 0.2 to 1.8 mGy.
• radioisotope is excreted in urine, and the bladder reservoir acts as a significant
source of exposure to the fetus.
• Therefore, patient should be encouraged to maintain a high-fluid intake and
void frequently.
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25. • Renography is a physiological approach and its safety has been demonstrated.
• However, physiological dilatation can be confused with pathological
obstruction in 10%–20% of patients
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27. Conservative Treatment
“expectant therapy for the expectant mother”
• 70%–80% of pregnant patients with symptomatic calculi will pass them
spontaneously with hydration, analgesia
• Indications for a more aggressive approach:
(1) obstruction of a solitary kidney
(2) sepsis
(3) colic refractory to drug therapy,
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28. • NSAIDs block prostaglandin synthesis - premature closure of the ductus
arteriosus in utero and, therefore, should be avoided
• preferred analgesic regime has been frequent, small doses of morphine
• morphine on chronic use - fetal narcotic addiction, intrauterine growth retardation,
and premature labor.
• codeine is teratogenic when used in the first trimester
• antibiotics of choice – penicillins, cephalosporins, Erythromycin
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29. • tamsulosin and nifedipine - used off label, but not FDA approved for use in
pregnancy
• smooth muscle relaxation benefit may prove less useful in pregnancy, as the
ureters are already physiologically dilated.
• tamsulosin is associated with sudden infant death syndrome.
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30. • Premature labor from renal colic is the most common obstetric complication of
urolithiasis.
• Standard tocolytic therapy with beta adrenergic agents halts premature labor
• risk of premature labor should cease completely with the passage or removal of
the stone.
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33. Ureteroscopy
• diagnostic and therapeutic; safely employable
• Contraindications:
(1) stone size > 1 cm
(2) multiple calculi
(3) a solitary kidney
(4) sepsis
Temporizing procedures should be considered in these situations.
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34. • Non urgent uretroscopy is best performed in 2nd trimester.
• Most distal ureteric stones can be retrieved with a stone basket
• Fragmentation can be accomplished safely with pulse-dye laser, holmium:YAG laser
or pneumatic lithotripsy
• Use of low dosed and pulsed fluoroscopy combined with lead shielding of the
patient’s pelvis can reduce total radiation exposure,
• Direct endoscopically visualized passage of the ureteroscope or USG guided
ureteroscopy - radiation-free methods.
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35. Other modalities..
• Percutaneous stone extraction should be deferred until the postnatal - prolonged
anesthesia and radiation (not absolutely contraindicated)
• Modified PCNL in the supine position with ultrasound guidance and limited
fluoroscopic use may be considered
• ESWL is contraindicated in pregnancy because of the potential disruptive effects of
the shock wave energy on the fetus- spontaneous miscarriage
• Open surgery remains a viable alternative
(premature delivery in 6.5%, 8.6%, and 11.9% during the first, second, and third trimester,
respectively)
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36. Asymptomatic Stones in Patients Contemplating
Pregnancy
• renal stones tend to become symptomatic during pregnancy.
• Therefore, the management of asymptomatic calculi in women of childbearing
age must be considered in order to avoid the risks of subsequent management
during a pregnancy.
• recurrent gross hematuria, documented stone growth, UTI, and recurrent renal colic
associated with a mobile calyceal stone are all indications for prophylactic treatment
in women of childbearing age
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37. Conclusions
• differential diagnosis of flank pain during pregnancy is expansive
• US combined with measurements of renal vascular resistance and ureteral jets appears
to be the ideal imaging
• isotope renography or MRU is useful in delineating the level and grade of
obstruction
• radiation-induced fetal abnormalities have not been reported below fetal absorbed
dose level of 0.1 Gy
• Judicious and selective use of LDCT appears to offer substantial diagnostic benefits
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