尿管狭窄：狭くなった尿管が腎臓を静かに破壊する仕組み

最終更新日: 8月 25, 2026

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The ureter is the narrow tube carrying urine from a kidney down to the bladder — about the width of a drinking straw. A ureteral stricture is a scarred segment that has narrowed it. Urine backs up, the kidney above swells, and over time that kidney can be damaged.

This is not the same as a 尿道狭窄症, which affects the tube from the bladder to the outside and causes a weak stream. The names are confusingly similar and the conditions are entirely different. This page is about the ureter.

• タイ・バンコク病院 泌尿器科センター オンライン予約 02-310-3009 bhquro@bdms.co.th
• サミティベート・シラチャ病院(チョンブリ) 088-022-1445

The reason this condition is dangerous

This was missing from the earlier version of this article and is the most important thing on the page.

A ureteral stricture frequently causes no symptoms at all. You have two kidneys. When one is gradually obstructed, the other compensates so completely that blood tests stay normal and nothing feels wrong. There is no pain, because the obstruction developed slowly rather than suddenly — unlike a stone, which announces itself violently.

Meanwhile the pressure inside the obstructed kidney destroys it quietly, over months. By the time anything is noticed, function on that side may be substantially or entirely gone, and lost kidney function does not come back.

That is the entire argument for a piece of advice worth taking seriously: if you have had ureteroscopy for a stone, pelvic or abdominal surgery, or radiotherapy to the pelvis, attend the follow-up scan even though you feel completely well. Feeling well is not evidence that the kidney is well.

Symptoms, when there are any

• A dull ache in the flank or side, sometimes worse after drinking a lot.
• Repeated urinary infections, or infections that keep returning on the same side.
• 尿に血が混じる。
• A rise in kidney blood tests — though usually only when both sides are affected, or when there is only one working kidney.
• Very often, nothing whatsoever, with the narrowing found on a scan done for another reason.

What causes it

• 結石 — both a stone impacted against the ureteric wall for a long period, and the instruments used to treat it. This is among the commonest causes.
• Surgery near the ureter — gynaecological, colorectal or vascular. The ureter runs close to a great deal, and it can be injured directly or lose its blood supply from dissection nearby, with the narrowing appearing weeks or months later.
• Radiotherapy to the pelvis, sometimes many years afterwards.
• Cancer — of the urinary tract itself, or a tumour outside it pressing on or invading the ureter, cervical and colorectal cancers among them. Establishing whether cancer is involved is one of the first priorities.
• Fibrosis around the ureter — from endometriosis, from an aortic aneurysm, or from retroperitoneal fibrosis, which can trap both ureters at once.
• 結核, which scars the urinary tract and remains relevant in this region. It is also a cause of 尿中の白血球が陰性で培養検査, and finding it requires asking the laboratory for it specifically.
• 特定できる原因はありません, in a proportion of cases.

The two questions that decide everything

1. Is there cancer behind this? A narrowing caused by a tumour is a different problem requiring different treatment, and it must be excluded rather than assumed absent.
2. Is this kidney worth saving? If it still works, the aim is to relieve the obstruction and preserve it. If it has already been destroyed, reconstructing the ureter achieves nothing, and the question becomes whether the dead kidney needs removing at all — often it does not, unless it is causing infection, pain or high blood pressure.

The tests that answer them

• 超音波 — shows whether the kidney is swollen, and is usually where the problem is first spotted.
• CT画像 — shows where the narrowing is, how long it is, and what is around it, including a tumour.
• A renal function scan, sometimes called a renogram or MAG3 scan. This is the test that matters most and the one patients most often have not had. It measures how much of your total kidney function each kidney is contributing, and whether urine is genuinely obstructed or merely draining slowly through a wide but floppy system. A swollen kidney on ultrasound does not by itself prove obstruction; this scan is what settles it, and its result decides between reconstruction, observation and removal.
• Ureteroscopy with biopsy or urine cytology, where a tumour within the ureter is a possibility.

治療

The earlier version of this article described ureteral stricture as generally a lifelong problem. That is unduly pessimistic and has been corrected — a well-selected reconstruction cures the narrowing definitively in a great many people. What is true is that some strictures, particularly long ones, those caused by radiation, and those in people whose general health limits major surgery, are managed rather than cured.

• 経過観察, where the kidney contributes little, nothing is causing symptoms, and surgery would risk more than it gains. This is a legitimate decision, not a failure to treat — but it is made on the scan result, not on how well someone feels.
• A ureteric stent — an internal tube keeping the ureter open. Effective and quick, and the usual first step in an emergency, but it needs changing every few months and many people find it uncomfortable. It is a holding measure more often than a destination.
• A nephrostomy — a tube through the skin into the kidney, used when a stent cannot be passed or when drainage is urgent.
• Endoscopic dilatation or incision — attractive because it is minor, but honest expectations matter: results are best for short, recently formed strictures where the blood supply is intact, and considerably less reliable for long or ischaemic ones. Recurrence is common.
• Surgical reconstruction — cutting out the narrowed segment and rejoining the ureter, reimplanting it into the bladder, bringing the bladder up to meet it, or patching the ureter with a graft. Increasingly done robotically, which reduces the size of the incision without reducing what can be achieved inside. This is the definitive answer for most strictures in a kidney worth saving.

緊急事態となる症状

An obstructed kidney that becomes infected is a urological emergency. Antibiotics alone are not enough — the system has to be drained urgently, and delay is dangerous. In an emergency in Thailand, call 1669.

• Fever or shaking chills with flank pain, particularly if you are known to have a narrowing or a stent — go to hospital the same day, not to a clinic the following week.
• Feeling profoundly unwell, confused, or faint alongside a fever.
• Passing little or no urine, especially if you have one kidney or both sides are affected.
• Severe flank pain with vomiting.
• A stent that was due to be changed and has been forgotten. A stent left in far beyond its due date encrusts, blocks and can be very difficult to remove — this is one of the commonest avoidable disasters in urology.

Frequently Asked Questions About Ureteral Stricture

I feel completely well. Does the narrowing still need treating?

Possibly, and feeling well does not answer the question. The other kidney compensates so effectively that a gradually obstructed kidney can be destroyed without causing any symptoms or abnormal blood tests. The decision rests on a renal function scan showing what that kidney is contributing and whether it is genuinely obstructed.

Is this the same as a urethral stricture?

No. A ureteral stricture narrows the tube between kidney and bladder and threatens the kidney. A urethral stricture narrows the tube from the bladder to the outside and causes a weak urinary stream. The names are similar and the conditions are unrelated.

Is it permanent?

Often not. Reconstruction cures the narrowing definitively in many people, and an earlier version of this article described the condition as generally lifelong, which was too pessimistic. Long strictures, those caused by radiation, and situations where major surgery is unwise are more often managed than cured.

Can it be fixed without open surgery?

Sometimes. Endoscopic dilatation or incision works best for short, recent strictures with an intact blood supply and is considerably less reliable otherwise, with recurrence common. Reconstruction is frequently performed robotically, which means a small-incision operation rather than a lesser one.

もし腎臓がすでに破壊されているとしたら？

Then reconstructing the ureter serves no purpose. A non-functioning kidney does not automatically need removing; it is taken out when it causes recurrent infection, pain or high blood pressure, and otherwise it is often left alone.

診察のご予約について

Dr. Soarawee Weerasopone is a fellowship-trained robotic and reconstructive urologist at Bangkok Hospital Headquarters, and also sees patients at Samitivej Sriracha Hospital in Chonburi on 088-022-1445. Bring the imaging itself rather than the reports where possible, along with details of any previous stone treatment or abdominal surgery — the operation note is often the single most useful document.

来院が難しい海外の患者さんを含め、バンコク病院の遠隔診療をご利用いただけます。事前に泌尿器科へ次のメールアドレスまでご連絡のうえ、ご予約ください: bhquro@bdms.co.th。サミティベート・シラチャー病院は対面診療のみです。費用に関するお問い合わせには病院が対応しており、本ウェブサイトでは対応しておりません。

免責事項: 本コンテンツは、Bangkok Hospital Headquarters に勤務する泌尿器科専門医(認定医)の Dr. Soarawee Weerasopone が執筆・監修したもので、教育目的のみを意図しています。個々の方に対する医学的助言、診断、処方ではなく、個人メッセージやソーシャルメディアを通じて助言、診断、処方を行うことはありません。Dr. Soarawee は公開のソーシャルメディアアカウントを運営しておらず、彼の名前で個別相談を提供するアカウントは詐欺です。タイで緊急の場合は、次の番号に電話してください 1669.