10.1 GU, Pregnancy, Perinatal, and Congenital Conditions

Facility outpatient coding for the AAPC Certified Outpatient Coder (COC) exam lives in same-day surgery (SDS), emergency department (ED), and observation records. Chapters N, O, P, and Q of ICD-10-CM produce first-listed diagnoses that support medical necessity on the UB-04, and they produce some of the fastest COC traps: staging chronic kidney disease (CKD) too coarsely, splitting a combination cystitis code, inventing laterality on a kidney stone, treating benign prostatic hyperplasia (BPH) as if obstruction were built in, dropping an O code onto a newborn, or dropping a P code onto the mother.

The FY 2026 ICD-10-CM Official Guidelines for Coding and Reporting (October 1, 2025 through September 30, 2026), issued by the Centers for Medicare & Medicaid Services (CMS) and the National Center for Health Statistics (NCHS) for the Cooperating Parties, still layer chapter-specific rules on top of Section IV outpatient sequencing. This OpenExamPrep chapter teaches those rules in hospital outpatient language. It is independent study material for COC candidates; it is not an AAPC, CMS, or Cooperating Party publication.

Chapter 14: Genitourinary conditions (N00–N99)

CKD stages are not interchangeable

ICD-10-CM classifies CKD by severity in category N18. Stage 2 is mild (N18.2). Stage 3 is moderate and splits: N18.30 stage 3 unspecified, N18.31 stage 3a, N18.32 stage 3b. Stage 4 is severe (N18.4). Stage 5 is N18.5. N18.6 is end stage renal disease (ESRD). If the provider documents both a numeric stage and ESRD, assign N18.6 only. N18.9 is unspecified CKD and is a last resort when the record never states a stage.

CKD almost never travels alone on a facility claim. Hypertensive CKD uses I12.9 (stages 1 through 4, or unspecified) or I12.0 (stage 5 or ESRD), then the N18 stage, because the I12 combination does not name the stage. Type 2 diabetes mellitus with diabetic CKD is E11.22 plus the N18 stage. Long-term insulin, when documented, is Z79.4. A functioning kidney transplant with residual CKD is the N18 stage plus Z94.0, Kidney transplant status—not an automatic transplant-complication T code. Dialysis dependence with ESRD is N18.6 plus Z99.2, Dependence on renal dialysis.

SDS example: a patient arrives for cystoscopy. The history lists hypertension, type 2 diabetes, and CKD stage 3b. First-listed is the reason for surgery (for example a bladder tumor). Additional diagnoses include I12.9, E11.22, and N18.32. Do not report N18.30 when 3b is stated, and do not report N18.6 unless ESRD is documented.

UTI and hematuria: look for a combination code first

N39.0, Urinary tract infection, site not specified, is correct only when the site is truly not stated. When the ED note says acute cystitis, the N30 family owns the case. N30.00 is acute cystitis without hematuria. N30.01 is acute cystitis with hematuria. N30.01 is a combination code: do not add R31.9, Hematuria, unspecified, or R31.0, Gross hematuria, on top of it. If culture identifies Escherichia coli as the cause of a disease classified elsewhere, add B96.20.

The trap is coding N39.0 plus R31.9 when the record already supports N30.01. A pregnant patient with a urinary tract infection is not an N-code first-listed case. Chapter 15 takes sequencing priority, so O23.40, Unspecified infection of urinary tract in pregnancy, unspecified trimester (or O23.41–O23.43 when the trimester is known) is first-listed, with a Z3A.- weeks-of-gestation code when weeks are documented. N39.0 does not replace the obstetric code.

Kidney and ureter stones: laterality is in the note, not in N20

FY 2026 still has no laterality expansion under N20. N20.0 is calculus of kidney, N20.1 calculus of ureter, N20.2 calculus of kidney with calculus of ureter, and N20.9 unspecified urinary calculus. A left ureteral stone treated with ureteroscopy is still N20.1. Do not invent a fifth character for side. Do not borrow an injury code such as S37.012A, Minor contusion of left kidney, initial encounter, for a medical calculus.

If the same SDS record documents hydronephrosis due to the stone, N13.2, Hydronephrosis with renal and ureteral calculous obstruction, is the combination code. Do not stack N20.0 and N13.30. Infection with obstruction is N13.6, Pyonephrosis, not N13.2. Bilateral stones still map to one N20 code; ICD-10-CM does not let you report the same diagnosis code twice for two sides when the category has no laterality.

BPH with obstruction versus without

N40.0 is BPH without lower urinary tract symptoms (LUTS). N40.1 is BPH with LUTS. N40.2 and N40.3 are the nodular-prostate pair (without LUTS and with LUTS). Obstruction is not built into N40.0. When the urologist documents BPH with bladder-outlet obstruction, assign N40.1 and add N13.8, Other obstructive and reflux uropathy. Retention is R33.8, frequency R35.0, nocturia R35.1, hesitancy R39.11, weak urinary stream R39.12, incomplete emptying R39.14, and urgency R39.15. Tabular notes at N40.1 tell you to use additional codes for those symptoms. SDS transurethral resection of the prostate (TURP) for BPH with obstruction and acute retention is first-listed N40.1, then N13.8 and R33.8.

Chapter 15: Pregnancy (O00–O9A) on the maternal outpatient record

Chapter 15 codes are used only on the maternal record, never on the newborn. They have sequencing priority over other chapters unless the provider documents that the pregnancy is incidental, in which case Z33.1, Pregnant state, incidental, replaces Chapter 15. Incidental is a provider statement, not a coder assumption from a positive test on the problem list.

Most O categories end with a trimester character. First trimester is less than 14 weeks 0 days, second is 14 weeks 0 days to less than 28 weeks 0 days, and third is 28 weeks 0 days until delivery. Use unspecified trimester only when weeks cannot be obtained. Add Z3A.- when the specific week is known. Completed weeks means full weeks: documentation of 39 weeks 6 days is still 39 completed weeks.

Supervision versus a complication

Routine outpatient prenatal care with no complication is first-listed Z34.- (for example Z34.00, Encounter for supervision of normal first pregnancy, unspecified trimester, or Z34.80 for a subsequent normal pregnancy). Do not pair Z34.- with Chapter 15 codes. High-risk prenatal visits use O09.- first (for example O09.511, Supervision of elderly primigravida, first trimester). Secondary O codes may be added when appropriate. When the encounter is for a complication and no delivery occurs, first-list that complication.

ED contrast: a patient at 22 weeks is seen for a right ankle sprain, and the obstetrician’s note states the pregnancy is incidental to the visit. First-listed is the sprain (for example S93.401A, Sprain of unspecified ligament of right ankle, initial encounter) plus Z33.1. If the same patient is observed for hyperemesis with metabolic disturbance at 11 weeks, first-listed is O21.1, Hyperemesis gravidarum with metabolic disturbance, not Z34.90 and not a Chapter 16 code.

Ectopic pregnancy and missed abortion in SDS and ED

Ectopic pregnancy lives in O00. Laterality is built into several subcategories. O00.101 is right tubal pregnancy without intrauterine pregnancy; O00.102 is left; O00.109 is unspecified tubal pregnancy without intrauterine pregnancy. Do not default to O00.109 when the operative report names the left tube. SDS laparoscopic salpingectomy for a left tubal ectopic at 8 weeks is first-listed O00.102, with Z3A.08 when 8 weeks is documented. That patient is the mother. Codes in P00.- describing a newborn affected by maternal conditions do not belong on her claim.

O02.1, Missed abortion, is the maternal code for early embryonic or fetal death with retention of the pregnancy tissue. ED or SDS suction dilation and curettage for missed abortion is first-listed O02.1, not a P code and not Z34.- supervision. Later intrauterine fetal death in a continuing pregnancy is maternal care for intrauterine death (O36.4-), still on the mother. P95, Stillbirth, is a newborn-record code and is not first-listed on a maternal outpatient claim. Incomplete spontaneous abortion without complication is O03.4; complete without complication is O03.9. Subsequent care for retained products after a prior complete-abortion discharge still follows the incomplete/retained-product instruction in the obstetric guidelines (O03.4 or O07.4 when there is no additional named complication).

Chapter 16: Perinatal (P00–P96) — who is the patient?

The perinatal period runs from before birth through the 28th day after birth. P codes are never used on the maternal record. Obstetric O codes are never used on the newborn record. Chapter 16 codes may continue throughout life if the perinatal condition is still present, but that permission does not move a P code onto the mother’s SDS, ED, or observation claim.

When the mother is the patient, code what is wrong with her. A maternal ED visit for a pregnancy complication is an O-code problem, not P05.- growth restriction or P07.- prematurity on the mother’s UB-04. Birth-record first-listed Z38.- (liveborn infant by place of birth and type of delivery) is assigned once, on the newborn, at the birth hospital—not on the mother’s outpatient claim and not on a later pediatric clinic visit.

Chapter 17: Congenital versus acquired (Q00–QA1)

Assign Q00–QA1 when a malformation, deformation, or chromosomal abnormality is documented, at any age. If the anomaly has been corrected, use a personal-history code such as Z87.74, Personal history of (corrected) congenital malformations of heart and circulatory system, rather than the Q code. Inherent manifestations of a named anomaly are not coded separately; extra manifestations that are not inherent are.

The classification often forbids coding a congenital form and an acquired form together (an Excludes1 note). An adult SDS patient with an unrepaired congenital ventricular septal defect is Q21.0, Ventricular septal defect, not I23.2, Ventricular septal defect as current complication following acute myocardial infarction. I23.2 is acquired after infarction. Congenital dislocation of the right hip is Q65.01; an acute traumatic right-hip dislocation is an S code such as S73.004A, Unspecified dislocation of right hip, initial encounter, not a Q code. If the record never says congenital or acquired, follow the Alphabetic Index default. Do not guess congenital because the patient is young, and do not guess acquired because the patient is 54.