腎臓と尿路は、一般的なもの（腎結石や尿路感染症）から複雑なもの（慢性腎臓病、水腎症、尿管狭窄）まで、幅広い疾患の影響を受けます。効果的な管理は、軟性尿管鏡検査（fURS/RIRS）、経皮的腎砕石術（PCNL）、バルーン拡張などの低侵襲内視鏡的泌尿器科処置への依存度が高まっています。本ガイドは、泌尿器科診療に最も関連性の高い解剖学、疾患、処置を網羅し、各ステップで使用されるシングルユース医療機器へのリンクを提供しています。
Anatomy of the Kidney & Urinary Tract
Adrenal Glands
Sit atop the kidneys. Produce hormones including cortisol and aldosterone, which influence kidney function and blood pressure.
Kidneys
Bean-shaped organs (~11 cm long) located in the retroperitoneum. Each contains ~1 million nephrons — the functional filtration units.
Renal Pelvis & Ureters
The renal pelvis collects urine from the calyces; the ureters (25–30 cm) transport it by peristalsis to the bladder.
Bladder & Urethra
The bladder stores up to ~500 mL of urine. The urethra carries it to the exterior; length varies (female ~4 cm, male ~20 cm).
Clinically Relevant Microanatomy
- • Nephron: Composed of the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct. Proximal tubule responsible for ~67% of solute/water reabsorption; primary target of ischaemic AKI.
- • Juxtaglomerular apparatus (JGA): Macula densa senses tubular sodium and regulates renin secretion — central to blood pressure homeostasis and the RAAS axis.
- • Uretero-vesical junction (UVJ): Acts as a physiological valve preventing reflux; most common site for stone impaction. Ureteroscopy access through the UVJ may require balloon or active dilation.
- • Pelvi-ureteric junction (PUJ): Second most frequent stone impaction site; PUJ obstruction often requires endopyelotomy or pyeloplasty.
Kidney Function
The kidneys are remarkable multi-functional organs. Far more than simple filters, they regulate the entire fluid balance of the body and produce vital hormones.
Filtration
Remove urea, creatinine, drugs, and waste from blood — approximately 125 mL filtered per minute (GFR)
Fluid & Electrolyte Balance
Regulate sodium, potassium, calcium, phosphate, and water balance through precise tubular reabsorption
Hormonal
Produce erythropoietin (EPO), activate vitamin D, and release renin — critical for blood pressure and red cell production
GFR-Based CKD Staging (KDIGO 2024)
* Albuminuria category (A1–A3) must always be combined with GFR staging for prognosis. KDIGO 2024 emphasises heat map risk stratification.
Kidney Stones (Nephrolithiasis)
Kidney stones are hard mineral deposits that form inside the kidneys when urine becomes concentrated. They vary in size from a grain of sand to several centimetres. Small stones may pass on their own; larger ones may require medical intervention.
Types of Kidney Stones
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Calcium Oxalate
Most common (80%). Associated with low fluid intake & high oxalate diet
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Uric Acid
~10%. Linked to gout, high-protein diet, dehydration
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Struvite
~10%. Caused by urease-producing bacteria; can form large staghorn calculi
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Cystine
Rare (<1%). Genetic disorder causing excess cystine excretion
Symptoms of Kidney Stones
| Stone Size | Location | Preferred Treatment (EAU 2024) | Instrument |
|---|---|---|---|
| <4 mm | Ureter / Renal | Watchful waiting / MET (α-blockers or CCBs) | — |
| 4–10 mm | Distal ureter | SWL or semi-rigid URS | UAS (e.g. Manawa FANS), laser fibre |
| 10–20 mm | Renal pelvis / calyx | SWL or flexible URS (fURS / RIRS) | UAS with suction; single-use scope |
| >20 mm | Renal | PCNL (standard or mini) | Nephrostomy balloon dilator (e.g. Tahina); nephrostomy access sheath |
| Staghorn | Complete renal pelvis | PCNL ± staged SWL | Large bore nephrostomy sheath; suction drainage |
Metabolic Workup Indications
24-hour urine collection (calcium, oxalate, citrate, uric acid, sodium, creatinine, volume) indicated for: recurrent stone formers, bilateral or multiple stones, children, family history, solitary kidney, or first-time stone in patient with CKD. Serum workup: calcium, PTH, uric acid, bicarbonate.
Obstruction & Hydronephrosis
Hydronephrosis is a swelling of one or both kidneys caused by a build-up of urine. This usually occurs because a blockage prevents urine from draining properly. Causes include kidney stones, strictures, enlarged prostate, or tumours.
Left untreated, obstruction can lead to permanent kidney damage. Treatment depends on the cause and severity — ranging from ureteral stents to surgical correction.
| Grade | Ultrasound Finding | Clinical Significance |
|---|---|---|
| Grade I | Mild renal pelvis dilatation only | Often physiological; monitor |
| Grade II | Pelvis + major calyceal dilatation | Investigate for obstructive cause |
| Grade III | All calyces dilated; cortex preserved | Intervention likely required |
| Grade IV | Cortical thinning (<2 mm) | Urgent drainage; long-term function at risk |
⚠️ Obstructed Infected Kidney — Urological Emergency
Obstructed pyonephrosis (infection proximal to obstruction) carries mortality rates of 20–40% if drainage is delayed. Urgent decompression via percutaneous nephrostomy or retrograde ureteral stenting must precede definitive stone treatment. Antibiotic therapy alone is insufficient — drainage is mandatory. Elective ureteroscopy should not be attempted on infected, obstructed systems.
Chronic Kidney Disease (CKD)
CKD is a gradual loss of kidney function over months or years. It is often silent in early stages but can progress to kidney failure requiring dialysis or transplantation. The most common causes are diabetes and high blood pressure.
Common Causes
- • Diabetes mellitus (T1 & T2)
- • Hypertension
- • Glomerulonephritis
- • Polycystic kidney disease
- • Recurrent obstructive uropathy
- • Chronic NSAID use
Warning Signs
- • Fatigue & weakness
- • Swollen ankles/legs (oedema)
- • Shortness of breath
- • Nausea / poor appetite
- • Foamy or dark urine
- • Persistent itching (pruritis)
Management Goals
- • BP control (<130/80 mmHg)
- • Glycaemic optimisation
- • RAAS blockade (ACEi/ARB)
- • SGLT2 inhibitors (CKD + T2DM)
- • Low-protein diet (G4–G5)
- • Nephrology referral
CKD & Urological Intervention — Practical Considerations
- • Contrast-induced nephropathy risk: use iso-osmolar contrast; pre-hydration; consider CO₂ urography in eGFR <30 mL/min/1.73m².
- • Nephrotoxic antibiotics (aminoglycosides, vancomycin) require dose adjustment; use with caution in eGFR <60.
- • Stone disease accelerates CKD progression — complete clearance and metabolic prevention are priority.
- • PCNL in solitary kidneys: suction drainage sheaths are preferred to minimise pyelovenous backflow and post-operative sepsis risk.
- • JJ stent dwell time: avoid >3 months; encrustation risk dramatically elevated in hyperoxaluria, hypercalciuria, and infection.
Ureteral Strictures
A ureteral stricture is a narrowing of the ureter that can impede normal urine flow from the kidney to the bladder. It may cause pain, recurrent infections, or kidney damage if untreated.
Common Causes
- • Prior urological procedures (ureteroscopy, stone treatment)
- • Radiation therapy to the pelvis or abdomen
- • Retroperitoneal fibrosis
- • Ischaemia (post-transplant, vascular)
- • Tumour compression or invasion
- • Congenital (PUJ obstruction)
Treatment Options
- • Balloon dilation: First-line for short, non-ischaemic strictures — using high-pressure ureteral balloon dilators
- • Endoureterotomy: Laser or cold-knife incision
- • JJ stenting: Temporary or long-term urinary diversion
- • Open / laparoscopic repair: Ureteroureterostomy, Boari flap, psoas hitch, ileal interposition for complex/long strictures
- • Ureteral reimplantation: For distal strictures
Balloon Dilation — Clinical Context
High-pressure balloon dilation (up to 20 ATM) with non-compliant balloon catheters (e.g. Tahina Ureteral) allows radially uniform force delivery across a stricture. Success rates of 50–80% in short (<1 cm), non-ischaemic, non-radiation-induced strictures. Ischaemic and radiation-induced strictures have higher recurrence rates (>50%); endoscopic balloon dilation serves as temporisation or repeated palliation in these cases. Kink-resistant shaft and hydrophilic distal coating are essential properties for negotiating tortuous ureters and tight strictures.
泌尿器科処置：尿管鏡検査、PCNL・低侵襲治療
When medication and watchful waiting are not enough, various minimally invasive procedures can treat kidney and urinary tract conditions safely and effectively. Here's a plain-language overview of the most common ones.
Ureteroscopy (URS / fURS)
A thin flexible or semi-rigid scope is passed through the urethra and bladder into the ureter or kidney. Stones can be fragmented with a laser and removed, or biopsies taken.
Flexible URS (RIRS) preferred for renal calculi >10 mm. Ureteral Access Sheaths (UAS) maintain access, reduce intrarenal pressure, and improve stone clearance. Active suction UAS (Manawa FANS) further reduces pyelovenous backflow and post-procedural sepsis. Single-use flexible ureteroscopes eliminate cross-contamination risk and maintain consistent optical performance.
Percutaneous Nephrolithotomy (PCNL)
A small incision is made in the back to create a direct tract into the kidney. A nephroscope removes large or complex stones. Standard PCNL (24–30 Fr), Mini-PCNL (14–20 Fr), Micro-PCNL (<14 Fr).
Tract dilation is accomplished using nephrostomy balloon dilators (e.g. Tahina Nephrostomy, 24Ch/30Ch, 17 ATM rated burst) or sequential fascial dilators. Balloon dilation is faster and associated with less blood loss vs. sequential. Suction nephrostomy access sheaths (Manawa Nephrostomy) reduce calyceal fluid distension, stone fragment migration, and systemic absorption of irrigation fluid — particularly valuable in renal insufficiency or complex staghorn stones.
Shock Wave Lithotripsy (SWL)
Non-invasive procedure using focused sound waves to break kidney stones into small fragments. Best for stones <10–15 mm in the renal pelvis or upper ureter.
Ureteral Stenting & Nephrostomy Drainage
A JJ (double-J) stent is placed inside the ureter to maintain drainage. A nephrostomy tube provides external kidney drainage when a retrograde approach is not possible (e.g. in obstruction with infection).
Nephrostomy access is guided by fluoroscopy or ultrasound; tract established by serial dilation or balloon dilation over a guidewire. Balloon dilators with radiopaque markers (e.g. Tahina Nephrostomy) enable real-time fluoroscopic confirmation of position. Post-PCNL nephrostomy tubes maintain tract patency for potential second-look procedures.
よくある質問：腎臓・尿路
腎結石の原因と治療法は？
腎結石（腎結石症）は、尿中にカルシウム、シュウ酸、尿酸、またはその他のミネラルが濃縮された際に形成されます。最も一般的な種類はシュウ酸カルシウム結石（約80%）です。4mm未満の小さな結石は自然排出されることが多いです。4〜20mmの結石は体外衝撃波砕石術（SWL）または尿管アクセスシースを用いた軟性尿管鏡検査（RIRS）で治療されます。20mm以上の結石は通常、経皮的腎砕石術（PCNL）が必要です。
軟性尿管鏡検査（RIRS）とは何か、いつ推奨されるか？
軟性尿管鏡検査（fURS）は、逆行性腎内手術（RIRS）とも呼ばれ、細い軟性カメラを尿道と膀胱を経由して腎臓に挿入します。10mmを超える腎結石に推奨されます。尿管アクセスシース（UAS）を尿管内に留置することで、医療機器のアクセスを維持し、腎盂内圧を低減し、結石排出を改善します。
PCNL（経皮的腎砕石術）とは何か？
経皮的腎砕石術（PCNL）は、20mmを超える大きな腎結石またはサンゴ状結石に対する低侵襲処置です。背部の小切開から腎臓に直接到達するトラクトを作成し、腎瘻バルーン拡張器を用いて拡張します。腎内視鏡により直視下で結石を破砕・除去します。吸引アクセスシースは腎盂内圧の低減と術後感染リスクの軽減に役立ちます。
水腎症とは何か、どのように治療されるか？
水腎症は、尿流の閉塞による片側または両側の腎臓の腫脹です。主な原因として腎結石、尿管狭窄、腫瘍が挙げられます。軽症例（グレードI〜II）は経過観察が可能です。重症例（グレードIII〜IV）では、永続的な腎障害を防ぐために尿管ステント留置または経皮的腎瘻造設による緊急ドレナージが必要です。
尿管アクセスシースとは何か？
尿管アクセスシース（UAS）は、軟性尿管鏡検査中に継続的なアクセスを提供するために尿管内に挿入される細いデュアルルーメンチューブです。腎盂内圧を低減し、灌流排出を改善し、繰り返しの医療機器挿入を可能にします。吸引機能付きアクセスシース（Manawa FANSなど）は結石破砕片と灌流液を能動的に排出し、術後感染リスクを低減し、術野の視認性を向上させます。