👤 By the CinnaRN Clinical Content Team🕐 Updated 2026-08-23🏷️ Physiological Adaptation🔖 Free to read, print, and share
Also known as: swollen kidney from backed-up urine · water on the kidney
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Use this quick-reference guide to spot, treat, and prevent Hydronephrosis on the NCLEX. Keep it handy during review and on exam day!
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📒 The 1-minute cheat sheet
📌 Mechanism
Obstruction → urine backs up
Pelvis/calyces dilate, ↑pressure
⚠️ Causes
Stones, BPH, tumor, stricture
🩺 Signs
Flank pain, ↓urine output
↑BUN/creatinine, hematuria
✅ Do
Relieve obstruction → catheter/stent
Monitor I&O, renal function
Untreated → permanent damage
📚 Hydronephrosis — full study notes
The cheat sheet above is your quick recall card. These notes go deeper — what it is, what to do first, what must be reported, and what to teach.
Hydronephrosis is distention and dilation of the renal pelvis and calyces due to obstructed urine outflow, causing back-pressure that can damage kidney tissue over time. Causes include kidney stones, strictures, tumors, an enlarged prostate (BPH), and congenital anomalies. Relieving the obstruction promptly is essential to preserve kidney function.
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Key points
Understand these first
It results from an obstruction anywhere along the urinary tract that backs urine up into the kidney.
Presentation depends on the cause and acuity: flank pain, decreased urine output, signs of UTI, or it may be silent and found on imaging.
Bilateral obstruction or obstruction of a solitary kidney can cause acute kidney injury and rising BUN/creatinine.
Treatment is aimed at relieving the obstruction (stent, nephrostomy tube, stone removal, treating BPH) before permanent damage occurs.
Prolonged or unrelieved obstruction leads to irreversible kidney parenchymal damage and loss of function.
After obstruction is relieved, a postobstructive diuresis can occur, requiring close fluid and electrolyte monitoring.
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Nursing priorities
What to do, in order
Monitor urine output strictly and assess for decreasing output or anuria.
Monitor renal function (BUN, creatinine) and fluid/electrolyte balance.
Assess and manage pain and prepare the patient for procedures to relieve obstruction (stent, nephrostomy).
Maintain patency of any urinary drainage device (catheter, nephrostomy tube, stent) and record drainage.
After relief of obstruction, monitor for postobstructive diuresis and replace fluids/electrolytes as ordered.
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Red flags — report now
Escalate immediately
Report anuria or sharply decreasing urine output, especially with a solitary or bilaterally obstructed kidney.
Report rising creatinine/BUN, severe flank pain, or fever with obstruction (obstructed infected system is an emergency).
Report a blocked or non-draining nephrostomy tube or catheter immediately.
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Labs & values
Numbers to know
Creatinine: 0.6-1.2 mg/dL (rises with obstruction)
BUN: 10-20 mg/dL (rises)
Potassium 3.5-5.0 mEq/L (monitor for derangement)
Urinalysis may show infection or hematuria depending on cause
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Patient teaching
What patients must know
Report decreased urination, flank pain, or fever promptly, since relieving the blockage protects the kidney.
If you have a nephrostomy tube or stent, keep it secure and report leaking, blockage, or no drainage.
Stay hydrated as directed and complete any treatment for the underlying cause (stones, prostate, infection).
Keep follow-up appointments to confirm the obstruction has resolved.
❓ Hydronephrosis: NCLEX FAQs
What are the priority nursing interventions for Hydronephrosis?
Monitor urine output strictly and assess for decreasing output or anuria. Monitor renal function (BUN, creatinine) and fluid/electrolyte balance. Assess and manage pain and prepare the patient for procedures to relieve obstruction (stent, nephrostomy). Maintain patency of any urinary drainage device (catheter, nephrostomy tube, stent) and record drainage.
What are the warning signs of Hydronephrosis a nurse must report?
Report anuria or sharply decreasing urine output, especially with a solitary or bilaterally obstructed kidney. Report rising creatinine/BUN, severe flank pain, or fever with obstruction (obstructed infected system is an emergency). Report a blocked or non-draining nephrostomy tube or catheter immediately.
What do I need to know about Hydronephrosis for the NCLEX?
It results from an obstruction anywhere along the urinary tract that backs urine up into the kidney. Presentation depends on the cause and acuity: flank pain, decreased urine output, signs of UTI, or it may be silent and found on imaging. Bilateral obstruction or obstruction of a solitary kidney can cause acute kidney injury and rising BUN/creatinine. Treatment is aimed at relieving the obstruction (stent, nephrostomy tube, stone removal, treating BPH) before permanent damage occurs.
What patient teaching is important for Hydronephrosis?
Report decreased urination, flank pain, or fever promptly, since relieving the blockage protects the kidney. If you have a nephrostomy tube or stent, keep it secure and report leaking, blockage, or no drainage. Stay hydrated as directed and complete any treatment for the underlying cause (stones, prostate, infection). Keep follow-up appointments to confirm the obstruction has resolved.
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Quick Tip
It results from an obstruction anywhere along the urinary tract that backs urine up into the kidney.