The upper pole of the kidney is the rounded, topmost portion of the organ, angled slightly toward the midline of the body and capped by the adrenal gland. Each kidney has two poles: an upper (superior) pole and a lower (inferior) pole, connected by a convex lateral border. While the term sounds like simple anatomical shorthand, the upper pole sits at a crossroads of clinical concern, from the way surgeons access kidney stones to the behavior of congenital anomalies and the decisions transplant teams face when arteries branch unexpectedly.
Where the Upper Pole Sits and What Surrounds It
Both kidneys lie behind the lining of the abdominal cavity, in a space called the retroperitoneum, one on each side of the spine. The upper pole points toward the midline and sits a bit higher than you might expect: the top of the right kidney typically reaches about the level of the twelfth rib, while the left kidney rides slightly higher because the liver pushes the right one down. Each kidney is wrapped in a fibrous capsule and cushioned by a thick layer of fat.1PubMed Central. Kidney anatomy: A Survey of Historical Illustrations and Methods of Depiction
The most distinctive neighbor of the upper pole is the adrenal gland, a small hormone-producing structure that sits on top of the kidney like a cap. Though the two organs are pressed closely together inside the same fatty envelope, a thin fibrous wall separates the adrenal gland from the kidney’s own capsule.2Surgery. Anatomy of the kidney and ureter – Section: The suprarenal glands That septum matters in surgery: it means the adrenal gland can usually be peeled away from the kidney without damaging either organ, a fact that comes into play during partial kidney removal.
Because of its high position, the upper pole is closely related to the lower ribs and the diaphragm, which separates the abdominal cavity from the chest. On the left side especially, the upper pole can tuck behind the eleventh or twelfth rib. That proximity to the chest wall is the main reason surgeons approach the upper pole with extra caution during certain procedures: a needle or instrument aimed at the top of the kidney can inadvertently cross into the pleural space surrounding the lung.
How the Kidney Reaches Its Position During Development
The kidneys do not start where they end up. During embryonic life, the kidneys form deep in the pelvis and then migrate upward over a span of roughly two weeks, from around the fifth to the seventh week of gestation. Researchers who examined serial sections of human embryos at this stage found that ascending kidneys were connected to the embryonic adrenal gland and nearby nerve clusters by a dense tissue band filled with nerve fibers from the major splanchnic nerve. This band appears rigid enough to support the mass of tissue that rises together during development.3The Anatomical Record. The Embryonic Ascent of the Kidney Revisited
At this early stage the kidney has no fatty capsule and no renal artery yet. It picks up its blood supply progressively as it climbs, discarding temporary feeding vessels along the way. The ascent also explains why the adrenal gland and the upper pole wind up in such close contact: they are literally traveling companions during development, bound together by that nerve-rich tissue bridge. When the ascent stalls partway, the kidney is left in an abnormally low position, a condition called renal ectopia, and the upper pole may sit where the lower pole of a normally positioned kidney would be.
Blood Supply to the Upper Pole
Most kidneys receive a single renal artery that branches from the aorta. Once it reaches the kidney, that artery divides into segmental branches, and the uppermost of these feeds the upper pole. In a straightforward case, the upper pole artery is simply the first branch off the main trunk as it enters the kidney’s central sinus.
Vascular anatomy around the upper pole is not always straightforward, though. Studies of children with duplex kidneys, where the kidney has two separate collecting systems stacked on top of each other, found that in about three-quarters of cases the kidney was still supplied by a single renal artery. In most of those, the artery split into its branches near the kidney’s surface rather than deep in the hilum.4PubMed. Anatomy and management of upper moiety vascular variation in children with duplex kidney Other patterns included accessory arteries coming off the aorta separately or branches piggybacking off the adrenal artery.
These variations become relevant during kidney transplantation. When a living donor kidney has more than one artery, the surgical team must decide how to handle the extra vessel. In a series of transplants involving allografts with multiple renal arteries, surgeons reconstructed either the upper pole artery or the lower pole artery to create a single inflow opening. None of the recipients in that series experienced vascular or urological complications, regardless of which pole’s artery was reconstructed.5Transplant International. Creating a Single Inflow Orifice From Living Donor Kidney Allografts With Multiple Renal Arteries – Section: Results A separate case series focusing specifically on upper pole artery reconstruction found that the mean diameter of these small arteries was around 1.8 mm, yet even at that size the repairs held up well, with no graft failures over more than a year of follow-up.6PubMed Central. Complex Surgical Reconstruction of Upper Pole Artery in Living-Donor Kidney Transplantation – Section: Results
Duplex Kidneys and the Upper Pole Moiety
A duplex kidney, one of the more common congenital variants, has two separate collecting systems instead of one. Each half is called a moiety, and the upper moiety drains the upper pole while the lower moiety drains the lower pole. The two moieties usually share a single outer capsule, so from the outside the kidney may look normal. The trouble tends to concentrate in the upper pole moiety.
When something goes wrong with a duplex kidney, it almost always involves the ureter draining the upper pole. That ureter can insert in an abnormal location, sometimes as far down as the urethra or, in girls, near the vaginal opening.7PubMed Central. Unilateral duplicated collecting system and ureter with severe hydroureteronephrosis and ectopic ureter insertion of upper pole moiety: A case report – Section: Case Presentation When the ureter inserts ectopically, urine backs up into the upper pole, dilating the ureter and the collecting system and potentially destroying the upper pole’s functional tissue over time. In imaging, this shows up as a ballooned-out upper pole with thin, stretched cortex that has lost the ability to filter blood effectively.8PubMed Central. Magnetic resonance urography in duplex kidney with ectopic ureteral insertion – Section: Abstract
The other classic upper pole problem in duplex kidneys is a ureterocele: a balloon-like swelling at the end of the upper pole ureter where it enters the bladder. Ureteroceles can obstruct the upper moiety, obstruct the lower moiety’s drainage as well, or even block the opposite kidney’s ureter. The treatment depends on how much function the upper pole still has. If it is essentially dead tissue, surgeons may remove just the upper pole and its ureter while leaving the functioning lower moiety intact, a procedure called upper pole heminephrectomy.
Horseshoe Kidneys and Pole Fusion
In a horseshoe kidney, the two kidneys are joined by a bridge of tissue called the isthmus. About 90% of the time, this fusion happens at the lower poles, producing the classic U-shape. Upper pole fusion is far less common and creates an inverted horseshoe configuration. When both poles fuse, the result is sometimes called a disc or pancake kidney.9Saudi Medical Journal. A rare case of a horseshoe kidney with a single left-sided ureter presented with recurrent urinary tract infection
Why the lower poles fuse so much more often than the upper poles comes down to embryonic geography. During the kidney’s ascent, the lower poles are closer to each other and to the midline, making it easier for the two developing kidneys to touch and merge. The upper poles angle outward and are separated by structures like the adrenal glands and major vessels, so they rarely come into contact. When upper pole fusion does occur, it tends to carry the same clinical complications as the more common lower pole variety: abnormal rotation of the kidneys, unusual ureteral courses, and a higher rate of kidney stones and urinary infections due to impaired drainage.
Surgical Access Through the Upper Pole
One of the most practical reasons clinicians care about the upper pole is percutaneous nephrolithotomy, a procedure used to remove large kidney stones by inserting instruments through the back directly into the kidney. When a stone sits in the upper pole or in a position best reached from above, the surgeon may need to puncture above the twelfth or even the eleventh rib. This supracostal approach offers a straighter path to the stone and, in some studies, a higher clearance rate for complex stones compared with lower approaches.10PubMed. Upper Pole Access for Prone Percutaneous Nephrolithotomy: Advantage or Risk? – Section: Results
The trade-off is the risk of crossing into the chest. The diaphragm and the thin membrane lining the lung (the pleura) lie just above the upper pole, and a needle that passes above the twelfth rib can nick or puncture this membrane. In one large series, the overall rate of pleural injury with upper pole access was about 14%, though only around 3% of patients actually needed a chest tube to drain the resulting fluid.11International Archives of Urology and Complications. Factors Predicting Pleural Complication Following Upper Pole Access Percutaneous Nephrolithotomy – Section: Results Another study of supracostal punctures reported a pleural breach rate of about 3%, with most cases managed either with a chest drain or by watchful waiting alone.12PubMed. Safety of supracostal punctures for percutaneous renal surgery – Section: Results The risk varies with which intercostal space is used: punctures above the eleventh rib are riskier than those above the twelfth, and left-sided procedures carry somewhat different risk profiles than right-sided ones because of the liver’s protective bulk on the right.
Surgeons weigh these risks against the benefit of a more direct route to the stone. For patients with a higher body mass index, the complication profile can actually shift: one study found that patients with a BMI of 30 or above had a lower rate of chest tube insertion after left-sided upper pole access, possibly because the thicker body wall keeps the puncture track further from the pleura.10PubMed. Upper Pole Access for Prone Percutaneous Nephrolithotomy: Advantage or Risk? – Section: Results
The Adrenal Gland Question During Partial Nephrectomy
When a tumor grows in or near the upper pole and the plan is to remove only the diseased portion of the kidney, a natural concern arises: should the adrenal gland come out too? Because the adrenal gland sits right on top of the upper pole, an upper pole tumor is the most likely scenario where the gland could theoretically be involved, either by direct invasion or by harboring a metastatic deposit.
The evidence suggests that routine removal of the adrenal gland is unnecessary, even for upper pole tumors. In a large series at a major referral center, the adrenal gland was preserved in more than 97% of partial nephrectomies. The surgeons only removed it when preoperative imaging showed a suspicious adrenal lesion or when the gland appeared involved during the operation itself. Even among those flagged cases, only about 13% of the suspicious adrenal nodules actually turned out to be cancerous.13PubMed. Management of the adrenal gland during partial nephrectomy – Section: Conclusions The fibrous septum separating the two structures, as noted earlier, generally keeps even upper pole cancers from spreading directly into the adrenal tissue.
Preserving the adrenal gland matters because the body relies on its hormones for blood pressure regulation, stress response, and electrolyte balance. Removing one adrenal gland is usually tolerable if the other is healthy, but unnecessary removal adds surgical time, increases the chance of hormonal imbalance in patients who may later need the other adrenal gland removed, and offers little oncological benefit based on available data.
How Imaging Identifies Upper Pole Problems
When you see the term “upper pole” in a radiology report or surgical note, it is almost always shorthand for describing the location of a finding: a cyst at the upper pole, a stone in the upper pole calyx, a mass arising from the upper pole cortex. Radiologists use ultrasound, CT, and MRI to map findings to specific kidney regions because location affects how a problem is approached. An upper pole stone may warrant supracostal access. An upper pole mass raises the adrenal gland question. An enlarged, poorly functioning upper pole moiety points toward a duplex system with obstruction.
On ultrasound, the upper pole can be tricky to visualize because the ribs and lung shadow the area. The sonographer often has to angle the probe steeply or ask the patient to take a deep breath, which pushes the kidney downward and brings the upper pole into view. On CT, the upper pole is easily identified in both axial (cross-sectional) and coronal (front-to-back) views, and the relationship between the upper pole and the adrenal gland is readily apparent. MRI is especially useful in children being evaluated for duplex kidneys because it can show the function of each moiety separately without ionizing radiation, helping the surgical team decide whether the upper pole is worth saving or too damaged to preserve.
Upper Pole Versus Lower Pole in Everyday Language
If you have been told you have a finding at the upper pole of your kidney, all it means in the most basic sense is that the finding is in the top third or so of the organ. The kidney does not have a sharp dividing line between upper, middle, and lower zones; these are descriptive regions rather than anatomically distinct compartments. The internal architecture of the kidney, its filtering units and collecting tubes, is essentially the same throughout. What makes the upper pole clinically distinct is not its internal structure but its external relationships: the adrenal gland overhead, the pleura a short distance above, and in duplex systems, a separate ureter that tends to misbehave.
People sometimes worry that an upper pole finding is inherently more serious than one at the lower pole. In general, location alone does not determine severity for most kidney conditions. A small cyst at the upper pole is no more concerning than one at the lower pole. A tumor at the upper pole is not automatically harder to treat, though the surgical approach may need adjustment to account for the ribs and the adrenal gland. The real question, regardless of pole, is always the nature of the finding itself: is it a simple cyst, a complex cyst, a solid mass, or a stone? The pole tells your doctor where to look and how to get there, not what the finding will turn out to be.