Urinary tract infections and kidney stones in pregnancy: Clinical sciences

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Introduction0:00–1:28

During pregnancy, the urinary tract undergoes several physiologic changes that increase an individual's risk of both urinary tract infections, or UTIs, and kidney stones, or nephrolithiasis.
Specifically, ureteral compression from the gravid uterus and ureteral relaxation from elevated levels of progesterone lead to urinary stasis and vesicoureteral reflux, increasing the risk of bacterial colonization and ascending infection.
Urinary tract infections in pregnancy exist on a spectrum with asymptomatic bacteriuria and acute cystitis affecting the lower urinary tract, while pyelonephritis affects the upper tract.
Screening and treating the former helps prevent pyelonephritis, which is associated with maternal sepsis, disseminated intravascular coagulation, or DIC, acute respiratory distress syndrome, or ARDS, and preterm labor.
Fetal complications like preterm birth and anemia may also occur. Now, kidney stones, which refer to hard deposits often made of insoluble calcium, occur as a result of the physiologic increased urine calcium excretion and elevated urine pH.
In severe cases, they may lead to ureteral obstruction, causing damage to the affected kidney or even become infected and create a renal abscess.
Your first step in evaluating a patient presenting with a chief concern suggesting a UTI or kidney stone is to perform an ABCDE assessment along with a primary obstetric survey to determine if they are stable or unstable.

Unstable patient1:28–2:07

If the patient is unstable, first stabilize the airway, breathing, and circulation. Obtain IV access and monitor maternal vital signs.
Additionally, assess the fetal status by monitoring the fetal heart rate.A labor evaluation may then be performed by testing for rupture of membranes and checking cervical dilation.
In this situation, you should be thinking about sepsis, urosepsis, or renal abscess.Now, when it comes to stable patients, start your assessment with a focused history and physical examination and obtain a urinalysis, or UA, and urine culture.

Asymptomatic Bacteriuria 2:07–4:16

Now, your patient might be asymptomatic, coming in for routine prenatal care. Screening for asymptomatic bacteriuria or ASB should be performed by obtaining a routine urine culture once, preferably early in pregnancy.
If a UA is performed it will be positive for leukocyte esterase and possibly nitrites. A urine culture will be positive, with a bacterial colony count of at least 100,000.
In this case, diagnose asymptomatic bacteriuria. Here’s a clinical pearl: Routine urinalysis to screen for ASB at each prenatal visit is not sufficiently sensitive for detection.
One caveat is that patients with hemoglobinopathy like sickle cell trait may have higher rates of ASB and cystitis, so you might want to screen them more often.Okay, when it comes to treatment, start with oral antibiotic therapy.
First-line antibiotics include cefalexin, fosfomycin, and nitrofurantoin. Once you get sensitivity results, tailor antibiotics to them.
You can consider repeating a urine culture to confirm the resolution of infection 1 to 2 weeks after antibiotic completion.Here are some more clinical pearls!
E. coli is the most commonly identified pathogen on urine culture, but it has high rates of antibiotic resistance, so avoid the use of empiric amoxicillin or ampicillin, and be sure to adjust therapy, if indicated, once urine culture sensitivity is available.
The presence of Group B streptococcus, or GBS, on urine culture at any colony count represents colonization. If the colony count is at least 100,000, treat the patient at the time of diagnosis with oral antibiotics and again during delivery with IV antibiotics as prophylaxis against early onset neonatal GBS infection.
If the colony count is less than 100,000, only treat during labor with IV antibiotics. Moving on, let’s talk about symptomatic patients.

Acute Cystitis4:16–5:42

History might reveal urinary symptoms like increased frequency, urgency, dysuria, hematuria, nocturia, or suprapubic pain.
UA will be positive for leukocyte esterase and possibly nitrites. Lastly, a urine culture will show a bacterial colony count of at least 100,000.
At this time, you can diagnose acute cystitis. Here’s a clinical pearl!
The absence of leukocyte esterase on UA is useful in ruling out a UTI but not sufficient to make a diagnosis as contaminants from the vulva or vagina can lead to a false positive result.
Nitrites, on the other hand, are the most specific finding for a UTI, but may not be present in all cases, as not all bacteria produce them.
As before, start with oral antibiotics and consider a test of cure versus simply monitoring for resolution of symptoms. If symptoms persist, repeat a urine culture.
For patients with recurrent UTIs, defined as at least two UTIs during pregnancy, you can consider antibiotic prophylaxis for the duration of the pregnancy, ideally with a lower dose once daily.
And another clinical pearl! In the presence of symptoms, it can be appropriate to treat patients even with colony counts as low as 100 of a single organism.Okay, back to history.

Pyelonephritis 5:42–7:36

Some patients might present with systemic symptoms like a fever of 38 degrees Celsius or higher and nausea and vomiting, as well as urinary symptoms, like flank pain and costovertebral angle tenderness, dysuria, and increased frequency and/or urgency.
UA shows leukocyte esterase and possibly nitrites, proteinuria, and/or microscopic hematuria; while urine culture reveals a colony count of at least 100,000.
With these findings, suspect pyelonephritis.Here’s a clinical pearl! If your patient has systemic symptoms obtain a urine microscopy, which will show pyuria.
Next, obtain a CBC, to assess for systemic evidence of infection. You may note leukocytosis, bandemia, thrombocytopenia, or anemia.
At this time, you can diagnose pyelonephritis. Treatment includes admission to the hospital, IV fluid hydration, and IV antibiotics, such as ampicillin, gentamicin, or ceftriaxone.
Be sure to evaluate the response after 72 hours. If there’s an inadequate response to empiric antibiotics, think about bacterial resistance and consider an alternative antibiotic.
Make sure to reconcile medication use based on the sensitivities received from the urine culture. You may also consider a renal ultrasound to rule out other pathology, such as nephrolithiasis.
Alternatively, if there is an adequate response, switch to oral antibiotics based on culture sensitivities for a total of 14 days.
Remember that nitrofurantoin does not reach therapeutic levels in the kidney, so it’s not a good choice for pyelonephritis.
After antibiotic completion, obtain a test of cure and consider daily suppressive therapy for the remainder of pregnancy.
Finally, let’s talk about the last set of findings. Patients might report renal colic, which is a sudden acute pain that typically starts near the costovertebral angle and extends anteriorly and inferiorly towards the groin.

Nephrolithiasis7:36–10:04

Renal colic is associated with urinary tract obstruction due to a stone. Additionally, history might reveal nausea and vomiting, as well as urinary symptoms of flank pain, dysuria, and hematuria.
A UA will show red blood cells and a urine culture will have no bacterial growth. Your next step is to obtain a renal ultrasound.
The ultrasound might show hydronephrosis that exceeds the expected changes for pregnancy. But if there’s no evidence of stones and both ureteral jets are visible on bladder ultrasound, consider an alternative diagnosis.
Here’s a high-yield fact! Hydronephrosis is thought to be related to compression of the urinary tract system from the gravid uterus, as well as progesterone's effects on the ureter, and is more commonly visualized on the right side due to the position of the right ureter in relation to iliac and ovarian vessels.
It’s a common physiologic change most often observed starting in the second trimester of pregnancy. On the other hand, renal ultrasound may show hydronephrosis beyond expected for pregnancy; you may also see evidence of a stone with posterior shadowing.
Stones on ultrasound will also exhibit ‘twinkle artifact’ when assessed with Doppler flow, and you may also see the absence of a ureteral jet on the affected side.
If you see these things, you can diagnose nephrolithiasis. Start the treatment with conservative management including analgesia with small, frequent doses of morphine; and hydration.
Keep in mind that, if the stone measures at least 1 cm on ultrasound, conservative management is less likely to be successful.
Next, assess your patient’s response including passage of the stone and their pain. If there is an inadequate response, obtain a urology consultation and consider medical management with calcium channel blockers or alpha blockers.
These medications cause relaxation of the ureteric smooth muscle and may allow spontaneous passage of stones. Additionally, consider a ureteral stent, percutaneous nephrostomy, or ureteroscopic stone removal.
Alternatively, if your patient has an adequate response, continue conservative management until symptoms resolve. Alright, as a quick recap… If you’re dealing with an asymptomatic pregnant patient with positive UA and urine culture, think about asymptomatic bacteriuria and manage with oral antibiotics.

Review10:04–10:49

Patients with urinary symptoms and positive urinalysis and culture have acute cystitis, which requires oral antibiotics.
If they also have systemic symptoms, you might be dealing with pyelonephritis, which is managed with IV antibiotics. Finally, for patients with renal colic and negative cultures, obtain a renal ultrasound to check for kidney stones.
If you see any, start management conservatively. If that doesn’t work, consider medical management or placing a ureteral stent, percutaneous nephrostomy, or ureteroscopic stone removal.
Urinary tract infections and kidney stones in pregnancy | Osmosis